SEC Form 424B3 filed by Kyivstar Group Ltd.

Filed Pursuant to Rule 424(b)(3)
Registration No. 333-287802

PROSPECTUS SUPPLEMENT No. 3
(to prospectus dated July 22, 2025)

KYIVSTAR GROUP LTD.

up to 7,666,667 common shares underlying warrants

This prospectus supplement updates, amends and supplements the prospectus dated July 22, 2025 (the “Prospectus”) which forms a part of our Registration Statement on Form F-4 (Registration Statement No. 333-287802). This prospectus supplement is being filed to update, amend and supplement the information previously included in the Prospectus with the information attached to this prospectus supplement.

This prospectus supplement updates, amends and supplements the information in the Prospectus and is not complete without, and may not be delivered or utilized except in combination with, the Prospectus, including any amendments or supplements thereto. This prospectus supplement should be read in conjunction with the Prospectus and if there is any inconsistency between the information in the Prospectus and this prospectus supplement, you should rely on the information in this prospectus supplement.

Our common shares are trading on the Nasdaq Stock Market LLC (“Nasdaq”) under the symbol “KYIV.” On November 7, 2025, the last reported sale price of our common shares was $12.16 per share.

Investing in our securities involves a high degree of risk. See “Risk Factors” beginning on page 22 of the Prospectus for a discussion of information that should be considered in connection with an investment in our securities.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if the Prospectus or this prospectus supplement is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus supplement is November 10, 2025.

THIRD QUARTER 2025 EARNINGS RELEASE

3Q25 HIGHLIGHTS

CONTENTS

3Q25 OVERVIEW

Kyiv, November 10, 2025 – Kyivstar Group Ltd. (“Kyivstar” or the “Group”), Ukraine’s leading digital operator, today announces selected unaudited financial and operating results for the third quarter ended September 30, 2025.

KYIVSTAR: 3Q25 KEY HIGHLIGHTS

Note:

Notice: Please see Attachment A for reconciliations to Kyivstar’s non-GAAP measures and Attachment D for a detailed description of such measures.

3Q25 GROUP PERFORMANCE

In the third quarter of 2025, Kyivstar delivered revenue growth of 20.9% YoY to UAH 12.3 bn, underscoring the Group’s ability to capture a growing share of consumer spending. Performance was driven by continued improvements in ARPU growth, rising engagement across digital platforms, and the transition to a new value-sharing model of the TV partnership into a platform-rental agreement, enhancing Kyivstar’s customer-facing role.

Revenue breakdown

Telecom revenue grew 9.0% YoY to reach UAH 10.9 bn in 3Q25, driven by continued ARPU expansion supported by disciplined pricing adjustments, rising mobile data consumption, and continuing migration of users to 4G networks. The Group’s sustained network investments and distinctive digital ecosystem continue to underpin strong subscriber engagement and operational resilience, even amid the ongoing war-related disruptions.

Direct digital revenue soared more than fivefold to reach UAH 1.5 bn in 3Q25, now accounting for 11.9% of total revenue. Growth was driven by the acquisition of Uklon, continued momentum across Helsi’s digital healthcare platform, rising demand for enterprise solutions such as big data services, and an expanding digital subscriber base.

TELECOM revenue, ARPU climb on 4G migration and multiplay

Mobile revenue growth remained strong during the quarter thanks to further deepening of customer engagement and continued positive momentum across key metrics.

Key subscriber and usage Data

Multiplay subscriber expansion

Through our multiplay strategy, we aim to consistently increase our multiplay subscriber rate (defined as users that have purchased (i) voice, (ii) 4G data plans, and (iii) at least one digital application, for example Helsi, Kyivstar TV, Uklon or MyKyivstar) by cross-selling our products and services. Our customers can select these digital services, which we call “superpowers,” as add-ons to their paid plans. We have seen a consistent upward trend in ARPU on the back of an increase in multiplay customers who also typically exhibit lower churn rates. Multiplay customers grew 24.8% YoY to 6.6 mn as of September 30, 2025, now representing 31.7% of the total one-month active user base. Multiplay revenue increased 44.5% YoY in UAH terms (43.2% YoY in USD).

DIRECT DIGITAL SERVICEs fuel growth

Kyivstar’s digital platforms continued to scale rapidly in the third quarter. Total digital monthly active users reached 13.5 mn (+49.4% YoY), reflecting both organic adoption and the consolidation of Uklon. The growing user base spans health, mobility and entertainment services, providing the Group with daily, high-frequency touchpoints, in addition to traditional telecom interactions. The breadth of engagement across these platforms is turning Kyivstar into the provider of a digital ecosystem, embedding the Group deeper into its customers’ everyday lives.

Digital monthly aCTIVE users

Direct digital revenue rose 531.3% YoY to UAH 1.5 bn in 3Q25, increasing its contribution to total revenue from 2.3% in 3Q24 to 11.9% in the third quarter. Growth was driven by the first-time consolidation of Uklon, continued expansion of Helsi’s digital healthcare services and strong uptake of Kyivstar TV.

DIRECT Digital revenue by PLATFORM

Uklon

The Uklon acquisition, effective April 2, 2025, contributed UAH 1.0 bn in revenue and UAH 378 mn in EBITDA in 3Q25. The platform recorded strong growth in trip volumes, average fare per ride and digital engagement, strengthening Kyivstar’s foothold in everyday mobility and reinforcing its ecosystem of services that extend beyond core telecom services.

Uklon: Key financial and operating metrics

Note: Uklon 3Q24 operating metrics are based on management reports from 2024 (pre acquisition).

Digital Enterprise: Big Data and Cloud Services

For 3Q25, our big data and cloud services generated UAH 222 mn in revenue, up 80.5% YoY (USD 5.4 mn, up 78.4% YoY). The growth was driven by large-scale big data analytics products and solutions, AdTech, cloud productivity and collaboration services, and API-based connectivity and data-exchange services.

We offer a comprehensive B2B hub as well as a big data and an advertising technology (“AdTech”) platform. Our B2B hub offers machine-to-machine (“M2M”) and cloud solutions, real-time kinematic positioning, cybersecurity services, an M2M SIM management platform and a digital marketplace – including 600 different cloud services. The real-time kinematic service alone now has more than 1,400 subscribers. Adwisor, our AdTech self-service platform, plays a central role in the Ukrainian advertising ecosystem with more than 2,500 registered clients. The platform is specifically designed for B2B customers, enabling seamless campaign management, targeted audience engagement and data-driven optimization.

Kyivstar Tech

Kyivstar Tech is a technology company that serves as the key provider of IT and digital services for the other companies in the Group, as well as providing limited IT and digital services to external enterprises. The company now has more than 800 software developers and data scientists.

Kyivstar TV

Kyivstar TV recorded 2.1 mn MAUs (+31.7% YoY), driven by exclusive sports rights, Ukrainian-language content, and the inclusion of new devices (e.g. Xbox, Smart TVs, PCs). Provided both as a mobile OTT internet application and a fixed/IPTV broadband service, Kyivstar TV is the largest media streaming service in Ukraine by number of users. As of September 30, 2025, 34.4% of our broadband customers were also digital TV users. The service’s role in users’ entertainment choices continues to expand, with user sessions rising 30.7% YoY in 3Q25 to 670 mn and the number of minutes watched daily by active OTT users having climbed 21.1% YoY to 244 mn.

Kyivstar does not license or create any content; rather, we sell digital TV services on our branded platform in cooperation with PLUS TV LLC. The TV partnership was revised as of September, enhancing Kyivstar’s role and direct customer engagement in the provision of the “Kyivstar TV” service.

Helsi

Helsi is Ukraine’s leading health-tech platform, recording 2.5 mn MAUs (+5.6% YoY) as of 3Q25. Growth was supported by the launch of new family and individual medical care subscription plans, as well as the expansion of enterprise contracts with hospitals and other corporates. Helsi has added new services to its subscription model, such as analysis and telemedical consultations, and launched “Helsi Superpower” for Kyivstar users in September.

Helsi is deeply embedded in Ukraine’s eHealth ecosystem, which powers appointment scheduling, prescriptions, and health records management. This integration creates high switching costs and makes Helsi indispensable for both patients and providers. It also demonstrates Kyivstar’s dedication to ESG matters, as access to high-quality, digital healthcare is a national priority during wartime.

As of September 30, 2025, Kyivstar had approximately 29 mn registered patients who were able to access more than 1,600 public and private clinics and over 38,000 medical professionals.

CAPITAL EXPENDITURE

Capex for 3Q25 was UAH 3.7 bn (USD 89 mn) with an LTM capex intensity of 29.1%. Kyivstar maintained high investment levels while generating strong free cash flow, underscoring the Group’s commitment to investments that fulfill license requirements and sustain network quality and resilience amid the war.

LIQUIDITY AND CAPITAL STRUCTURE

Kyivstar reported UAH 19.5 bn in cash and cash equivalents as of September 2025. Bonds and loans outstanding reflects the debt to VEON and Ukraine Tower Company LLC (“UTC”). Lease liabilities associated with towers transferred to UTC are fully recognized under IFRS 16.

STRATEGIC DEVELOPMENTS

On August 14, 2025, VEON Ltd., a global digital operator and then parent company of Ukraine’s leading digital operator JSC Kyivstar, and Cohen Circle Acquisition Corp. (“Cohen Circle”), a special purpose acquisition company, announced the closing of the business combination that resulted in the listing of Kyivstar on Nasdaq Stock Market (“Nasdaq”) following the receipt of approval from Cohen Circle shareholders at the extraordinary general meeting held on August 12, 2025. As a result of the closing of the business combination, Kyivstar began trading its shares and warrants on the Nasdaq on August 15, 2025 under the ticker symbols “KYIV” and “KYIVW”, respectively, thereby becoming the first and only Ukrainian company listed on a US stock exchange. VEON held an 89.6% stake in Kyivstar as of the closing of the business combination.

On August 12, 2025, Kyivstar successfully conducted a test of satellite and terrestrial network integration using Starlink Direct to Cell technology. This is the first field test of Starlink Direct to Cell in eastern Europe. During the pilot in the Zhytomyr region, Kyivstar President and JSC Kyivstar CEO Oleksandr Komarov and Ukraine’s Minister of Digital Transformation, Mykhailo Fedorov, exchanged messages directly via Starlink Direct to Cell satellite service using regular 4G-enabled smartphones. The successful exchange confirmed the technology’s viability for Ukraine. Launch of first commercial services is due in December.

Kyivstar continues to advance its large language model (“LLM”) project in partnership with Ukraine’s Ministry of Digital Transformation and the WINWIN AI Centre of Excellence. In 3Q25, we established the project’s strategy, accelerating hiring, and established a legal framework for transferring datasets. This joint project aims to develop Ukraine’s first LLM trained deliberately on Ukrainian-language data. The cooperation memorandum builds on VEON’s and Kyivstar’s pledge to invest USD 1 bn to rebuild Ukraine’s digital infrastructure over 2023-2027. In addition to capturing the full range of Ukrainian dialects, terminology, history, and cultural context, the project is designed to ensure that sensitive national data is securely stored and processed within Ukraine, a critical requirement for sectors such as government, defense, healthcare, and financial services. The LLM will also serve as the foundation for AI-powered products and services, including legal and regulatory analysis tools, as well as specialized AI applications across both public and private sectors and in fields including education, finance, and health. The model is expected to deliver more accurate, relevant, and actionable insights for Ukrainian users than general-purpose global models. The first version of the Ukrainian LLM is scheduled for release by December 2025.

PRESENTATION OF UNAUDITED FINANCIAL RESULTS

Kyivstar’s results presented in this document are, unless otherwise stated, based on International Financial Reporting Standards (“IFRS”) as issued by the International Accounting Standards Board (“IASB”) and have not been externally audited or reviewed.

Certain amounts and percentages that appear in this document have been subject to rounding adjustments. As a result, certain numerical figures shown as totals, including those in the tables, may not be an exact arithmetic aggregation of the figures that precede or follow them.

The non-IFRS information disclosed in the document, including, among other things, EBITDA, EBITDA margin, Adjusted Net Profit, Adjusted EPS, LTM Equity Free Cash Flow, capex and capex intensity trends, is defined in Attachment D and reconciled to the comparable IFRS information in Attachment A.

UNAUDITED CONDENSED CONSOLIDATED INCOME STATEMENT

Operating (loss) / profit was impacted by non-cash charge of USD 162 mn associated with the Kyivstar listing. This expense represents a one-time, non-cash compensation for a stock exchange listing service equal to the excess of the fair value of the shares transferred compared to the fair value of the net assets received.

Net finance costs amounted to USD 16 mn, an increase primarily due to lower deposit income following the redemption of USD-denominated Ukrainian sovereign bonds.

Other non-operating (loss) / gain, net was USD 6 mn, an increase of USD 5 mn YoY. This increase was mainly driven by the fair value revaluation impact related to outstanding warrants. Under IFRS, these warrants are measured at fair value through profit or loss and revalued at each reporting period end. The valuation is based on the market price of the warrant at the reporting date, which may result in non-cash gains or losses in the income statement from one period to the next. However, these fluctuations have no impact on cash flows or the company’s underlying operating performance.

Net foreign exchange (loss) / gain, was USD 1 million, representing a USD 15 million change from 3Q24. The decline was largely attributable to foreign exchange gains recognized on the revaluation of USD-denominated bonds in 3Q24 which were subsequently redeemed.

Adjusted Net Profit for the period, which adjusts for the $162 mn listing expense, was down 11% YoY due to the factors discussed above as well as higher SG&A expenses, offsetting the $49m increase in revenue, 3Q25 loss for the period was USD 89 mn.

The basic and diluted earnings per share (EPS) are the same because the warrant exercise price exceeded the average market price of the shares during the reporting period, rendering the outstanding warrants out of the money. Accordingly, shares issuable upon warrant exercise are excluded from the diluted share count, resulting in identical basic and diluted shares outstanding and, therefore, identical basic and diluted EPS.

UNAUDITED CONDENSED CONSOLIDATED CASH FLOW STATEMENT

Note: please refer to attachment B for UAH denominated statement

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEET

Note: please refer to attachment B for UAH denominated statement

Upon listing, the Debt and derivatives started to reflect a current liability associated with the fair value of the outstanding Kyivstar warrants, at USD 31 mn as of September 30, 2025. Under IFRS, these warrants are measured at fair value through profit or loss and are measured at each reporting period end, with the valuation being driven by the market price of the warrant at the end of the quarter.

ATTACHMENTS

CONTENT OF THE ATTACHMENTS

ATTACHMENT A: RECONCILIATION TABLES

ATTACHMENT B: CONDENSED UNAUDITED FINANCIAL STATEMENTS IN UAH

UNAUDITED CONDENSED CONSOLIDATED INCOME STATEMENT

UNAUDITED CONDENSED CONSOLIDATED CASH FLOW STATEMENT

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEET

ATTACHMENT C: RATES OF FUNCTIONAL CURRENCIES TO USD

The unaudited condensed consolidated income statements and the unaudited condensed consolidated cash flow statements have been translated using the average exchange rates prevailing during each reporting period. In the unaudited condensed consolidated balance sheets, all assets and liabilities have been translated using the period-end exchange rates, and all resulting exchange differences have been recognized in net foreign exchange (loss) / gain. UAH translations throughout this release are included solely for the convenience of the reader and were calculated at the exchange rates set forth in the table above under the header “Closing rates”.

ATTACHMENT D: DEFINITIONS

4G users are mobile customers who have engaged in revenue-generating activity during the three months prior to the measurement date as a result of activities over fourth-generation (4G or LTE – long term evolution) network technologies.

Adjusted Net Profit is profit / (loss) for the period, excluding the impact of the one-time, non-cash charge of USD 162 mn recognized in 3Q25 related to the Kyivstar listing.

ARPU (average revenue per user) measures the monthly average revenue per mobile user. We generally calculate ARPU by dividing our mobile and digital service revenue during the relevant period (including data revenue, roaming revenue, MFS and interconnect revenue, but excluding revenue from connection fees, sales of handsets and accessories and other non-service revenue, but excluding revenue from fixed IPTV) by the average number of our mobile customers during the period and the number of months in that period.

Capital expenditures (capex) are purchases of property and equipment, new construction, upgrades, software, other long-lived assets and related reasonable costs incurred prior to the intended use of the non-current asset, accounted at the earliest event of advance payment or delivery. Purchases of licenses and capitalized leases are not included in capital expenditures.

Capex intensity is a ratio, which is calculated as last-twelve-month (LTM) capex divided by LTM total revenue.

Direct digital revenues include revenues from Kyivstar Group Ltd.’s proprietary digital platforms and services.

Doubleplay 4G customers are mobile customers who engaged in usage of our voice and data services over 4G (LTE) technology at any time during the one month prior to such measurement date.

EBITDA is a non-IFRS financial measure and is called Adjusted EBITDA. Adjusted EBITDA is a non-IFRS financial measure. Adjusted EBITDA should not be considered in isolation or as a substitute for analyses of the results as reported under IFRS We calculate Adjusted EBITDA as profit/(loss) for the period, before income taxes, depreciation, amortization, loss from disposal of non-current assets and impairment loss, financial expenses and costs, net foreign exchange gain/(loss), share of profit/(loss) of associates and joint ventures, and listing expense, which is also excluded from the calculation.

EBITDA margin is calculated as EBITDA (as defined above) divided by total revenue, expressed as a percentage.

Equity free cash flow is a non-IFRS measure and is defined as free cash flow from operating activities and proceeds from sale of business, less cash flow used in investing activities, excluding license payments, lease payments, cash outflows for business acquisitions, inflow/outflow of deposits, and financial assets, cash inflows from sale of business and proceeds from share issuance.

Gross debt is calculated as the sum of long-term notional debt and short-term notional debt, including capitalized leases.

Mobile customers (also - mobile subscribers) are generally customers in the registered customer base at a given measurement date who engaged in a mobile revenue generating activity at any time during the three months prior to such measurement date. Such activity includes any outgoing calls, customer fee accruals, debits related to service, outgoing SMS and MMS, data transmission and receipt sessions, but does not include incoming calls, SMS and MMS or abandoned calls. Our total number of mobile customers also includes customers using mobile internet service via USB modems and fixed-mobile convergence (“FMC”).

Multiplay customers are Doubleplay 4G customers who also engaged in usage of one or more of our digital products at any time during the one month prior to such measurement date. Effective 1Q25, 4G usage below the 100Mb threshold is included in Multiplay and Double Play 4G user count (excluded prior to 1Q25).

Net debt / (cash) is a non-IFRS financial measure and is calculated as the sum of interest-bearing long-term debt, including capitalized leases (unless specifically excluded) and short-term notional debt minus cash and cash equivalents and deposits, , long-term and short-term deposits. We believe that net debt / (cash) provides useful information to investors because it shows the amount of notional debt that would be outstanding if available cash and cash equivalents and deposits and long-term and short-term deposits were applied to repay such indebtedness. Net debt should not be considered in isolation as an alternative to long-term debt and short-term debt, or any other measure of our financial position.

Revenues from telecommunications services (“Telecom revenues”) are revenues generated by Kyivstar Group Ltd from providing telecommunication services. Telecommunication services refer to data, voice, connectivity, television, and similar services, regardless of medium of transmission, including transmission by satellite.

Total digital monthly active users (“MAU”) is a gross total cumulative MAU of all digital platforms, services and applications offered by an entity or by the Group and includes MAU who are active in more than one application.

DISCLAIMER AND NOTICE TO READERS

Kyivstar’s results and other financial information presented in this document are, unless otherwise stated, prepared in accordance with International Financial Reporting Standards (“IFRS”) as issued by the international Accounting Standards Board and have not been externally reviewed and/or audited. As such, you should not place undue reliance on this information. Also, certain amounts and percentages have been subject to rounding adjustments.

This presentation includes certain financial and operating measures, including Adjusted EBITDA, CAPEX excl. licenses and ROU and Uklon Adjusted EBITDA, that are not prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) or IFRS. These non-GAAP/non-IFRS measures, and other measures that are calculated using these non-GAAP/non-IFRS measures, are an addition, and not a substitute for or superior to measures of financial performance prepared in accordance with GAAP or IFRS and should not be considered as an alternative or substitute those determined in accordance with GAAP or IFRS. The Company believes these non-GAAP/non-IFRS financial measures provide valuable insights into key financial and business trends, offering management and potential investors a useful tool for evaluating the Company’s performance and comparing it with peers that report similar metrics. These non-GAAP/non-IFRS measures have limitations, including potential differences in definition from those used by other companies, which may affect comparability.

Our operations in Ukraine continue to be affected by the war. We are doing everything we can to protect the safety of our employees, while continuing to ensure the uninterrupted operation of our communications, financial and digital services. We are closely monitoring events in Ukraine, as well as the possibility of the imposition of further legal and regulatory restrictions, including sanctions and countersanctions, in connection with the ongoing war in Ukraine and any potential impact the war may have on our results, whether directly or indirectly.

This document contains “forward-looking statements”, within the meaning of the Private Securities Litigation Reform Act of 1995 .Such forward-looking statements may be identified by words such as “may,” “will,” “expect,” “plan,” “anticipate,” “potential,” “continue,” and other similar words. Forward-looking statements include, but are not limited to, statements relating to Kyivstar Group’s strategic plans, operating results, targets or financial positions; Kyivstar Group’s intended expansion of its digital experience, including through technologies such as artificial intelligence; and Kyivstar’s assessment of the impact of the war in Ukraine on its current and future operations and financial condition.

While the forward-looking statements included in this document are based on management’s best assessment, there are numerous risks and uncertainties that could cause Kyivstar Group’s actual results, plans and objectives to differ materially from those expressed, such as those risks discussed in the section entitled “Risk Factors” in Kyivstar Group’s final prospectus filed with the SEC on July 22, 2025, as such document may be amended or supplemented from time to time] and other public filings made by Kyivstar Group with the SEC. You are cautioned not to place undue reliance on these forward-looking statements. The forward-looking statements speak only as of the date hereof and we disclaim any obligation to update them, except to the extent required by law.

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