SEC Form 6-K filed by KT Corporation

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

OF THE SECURITIES EXCHANGE ACT OF 1934

For the month of August 2025

Commission File Number 1-14926

KT Corporation

(Translation of registrant’s name into English)

90, Buljeong-ro,

Bundang-gu, Seongnam-si,

Gyeonggi-do,

Korea

(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F:

Form 20-F ☒   Form 40-F ☐

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

KT 2Q25 Earnings Release

Disclaimer This presentation has been prepared by KT Corp. (the “Company”) in accordance with K-IFRS. This presentation contains forward-looking statements, which are subject to risks, uncertainties, and assumptions. This presentation is being presented solely for your information and is subject to change without notice. No presentation or warranty, expressed or implied, is made and no reliance should be placed on the accuracy, actuality, fairness, or completeness of the information presented. The Company has applied new accounting standard of K-IFRS 1115 as of Jan 1st, 2018 and K-IFRS 1116 ‘Leases’ as of Jan 1st, 2019. There are no obligation to apply the new standard to previous financial statements. If you have any questions related to this material, please contact the IR department. Tel: +82-70-4193-4036 2

Contents 1 2Q25 Highlights 2 Financial Highlights 3 Business Overview 4 Appendix

1 2Q25 Highlights Financials Significant increase in OP driven by real estate PJT*, CT and group portfolio growth (Unit: KRW) Cons. Revenue 7,427.4bn (YoY +13.5%) Sep. Revenue 4,772.8bn (YoY +4.9%) Operating Profit 1,014.8bn (YoY +105.4%) Operating Profit 468.7bn (YoY +30.6%) Shareholder return 2Q25 KRW 600 Share Dividend Announce KRW 250bn dividend amount 1 per share Buyback2 Procedure Dividend (Value-up plan) (YoY +20%) prior to record date(2Q~) 1)Record date: ‘25.7.30, 2)To be completed by Aug 13; cancelled once foreign ownership limit allows Management Strategy Transform into AICT company Secured AI Full Line-up KT developedMi:dm2.0/ Open-SourceLlama / MS Collaboration Models Won large-scale AI/IT project orders Securing of contracts from large/IT companies Introduced Genie TV AI Agent Powered by LLM3) based on MS Azure OpenAI Service Strengthening competitiveness through MS partnership SPC4) with ACC5) / Korean AI model to launch in 2H 3)Large Language Model 4)Secure Public Cloud 5)Azure Confidential Computing 4

Contents 1 2Q25 Highlights 2 Financial Highlights 3 Business Overview 4 Appendix

K-IFRS / Consolidated 1 Income Statement Revenue +13.5% YoY driven by growth in telecom, real estate, and cloud/DC businesses OP +105.4% YoY reflecting KT Group-wide efforts for profitability and gains from real estate sales (Unit: KRW bn) 2Q241Q252Q25QoQ YoY Operating Revenue 6,546.4 6,845.1 7,427.4 8.5% 13.5% Service Revenue5,776.65,700.4 5,817.8 2.1% 0.7% Sale of goods 769.8 1,144.7 1,609.6 40.6% 109.1% Operating Expense 6,052.46,156.36,412.64.2%5.9% Operating Income494.0688.81,014.847.3% 105.4% Margin 7.5% 10.1% 13.7% 3.7%p 6.1%p Margin1 8.6% 12.1% 17.4% 5.4%p8.9%p Non-op. Income/Loss62.723.1-39.9Turned to lossTurned to loss Income before taxes556.7711.8974.937.0%75.1% Net Income410.5566.8733.329.4%78.6% Margin6.3%8.3%9.9%1.6%p3.6%p EBITDA1,460.21,657.41,990.720.1% 36.3% Margin 22.3% 24.2% 26.8% 2.6%p 4.5%p 1) OP Margin1 = Operating Income/Service Revenue 6

K-IFRS / Consolidated 2 Operating Expenses OP. expenses +5.9% YoY, driven by higher cost of service and cost of goods sold(COGS), despite a reduction in labor cost (Unit: KRW bn) 2Q241Q252Q25QoQ YoY Operating Expenses 6,052.4 6,156.3 6,412.6 4.2% 5.9% Labor Cost 1,213.2 1,121.8 1,119.4 -0.2% -7.7% General Expense 2,708.3 2,655.8 2,639.7 -0.6% -2.5% - Depreciation 966.2 968.7 975.9 0.7% 1.0% Cost of Service 656.6 738.4 755.8 2.3% 15.1% Selling Expense 600.8 598.0 615.1 2.9% 2.4% Cost of Goods sold 873.5 1,042.3 1,282.6 23.1% 46.8% [Selling Expense (KT Separate)] (Unit: KRW bn) 2Q241Q252Q25QoQ YoY Selling Expense618.6625.5 655.8 4.9% 6.0% 7

K-IFRS / Consolidated Balance Sheet Net Debt/equity ratio +3.3%p YoY due to increased borrowings from subsidiaries (Unit: KRW bn) Jun. 30, 2024 Mar. 31, 2025 Jun. 30, 2025 QoQ YoY Assets 43,144.4 42,185.6 42,193.3 0.0% -2.2% Cash & Cash equivalents 3,786.7 3,133.0 3,794.4 21.1% 0.2% Liabilities 24,162.5 23,847.3 23,316.2 -2.2% -3.5% Borrowings 10,150.6 11,169.5 10,750.2-3.8%5.9% Equity 18,981.9 18,338.3 18,877.1 2.9% -0.6% Capital Stock 1,564.5 1,564.5 1,564.5 0.0% 0.0% Net Debt 6,363.9 8,036.5 6,955.8 -13.4% 9.3% Debt / Equity 127.3% 130.0% 123.5% -6.5%p -3.8%p Net Debt / Equity 33.5% 43.8% 36.8% -7.0%p 3.3%p 131.1% 134.9% 132.7% 127.0% 130.1% 129.8% 127.3% 130.0% 124.8% 122.5% 121.5% 122.8% 123.5% 115.4% Debt/Equity Net Debt/Equity 42.9% 46.6% 44.6% 43.8% 7.4% 40.6% 41.0% 38.5% 39.5% 38.5% 37.8% 33.5% 36.8% 30.3% 1Q22 2Q22 3Q22 4Q22 1Q23 2Q23 3Q23 4Q23 1Q24 2Q24 3Q24 4Q24 1Q25 2Q25 8

K-IFRS / Separate and major subsidiaries 4 CAPEX 1H25 Total CAPEX Execution: KRW 845.8bn (KT Separate), KRW 518.5bn (Major Subsidiaries) (Unit: KRW bn) 3,534 3,319 813 3,124 907 824 2,721 1,364 2,412 2,300 519 846 2022 2023 2024 1H25 KT Major Subsidiaries Major Subsidiaries’ CAPEX Includes Finance, Media, Cloud/DC, Real Estate, etc. KT Separate CAPEX Access network, Backbone Network, B2B and etc. 9

Contents 1 2Q25 Highlights 2 Financial Highlights 3 Business Overview 4 Appendix

K-IFRS / Separate K-IFRS / Separate 1 KT—Wireless • Wireless service revenue +1.6% YoY with increased 5G penetration (79.5%) and MNO subscribers • Continued efforts to differentiate products, distribution and pricing 2Q24 1Q25 2Q25 QoQ YoY Wireless 1,765.1 1,753.1 1,781.7 1.6% 0.9% Wireless Service 1,677.9 1,676.8 1,704.8 1.7% 1.6% Interconnection 87.2 76.3 76.9 0.8% -11.8% Wireless Subscribers (Unit: Thousands) 27,491 24,904 25,199 26,132 26,445 10,867 10,400 10,552 10,093 10,251 2,795 2,969 2,802 Handset(5G) 3,364 3,184 5,832 6,180 Hands (exc. 5G) 4,562 5,581 4,313 2nd device & IoT MVNO 7,134 7,203 7,182 7,259 7,649 2Q24 3Q24 4Q24 1Q25 2Q25 (Unit: KRW bn) 11

2 KT—Fixed Line K-IFRS / Separate• Broadband revenue +2.1% YoY, due to increase in GiGA subscribers and value-added services • Media rev. up 0.8% YoY backed by IPTV net subscriber adds and premium plans uptake (Unit: KRW bn) 2Q24 1Q25 2Q25 QoQ YoY Fixed Line 1,316.6 1,311.7 1,334.5 1.7% 1.4% Broadband 618.5 628.7 631.4 0.4% 2.1% Media 522.6 519.2 526.9 1.5% 0.8% Home Telephony 175.6 163.8 176.2 7.6% 0.4% IPTV Subscribers (Unit: Thousands) 9,423 9,440 9,449 9,438 9,490 2Q24 3Q24 4Q24 1Q25 2Q25 12

3 KT—B2B Services K-IFRS / Separate• B2B services rev. +4.5% YoY driven by balanced growth in corporate telecom and AI/IT services, despite continued streamlining of low-margin businesses (Unit: KRW bn) 2Q24 1Q25 2Q25 QoQ YoY B2B Service 882.7 892.2 922.7 3.4% 4.5% Corp.Broadband/Data Revenue (Unit: KRW bn) 335.4 338.3 327.0 324.2 325.1 YoY +3.5% 2Q24 3Q24 4Q24 1Q25 2Q25 ? Corp. Broadband/Data rev includes: Leased line, Kornet, VPN, Global data Revenue of AI/IT (Unit: KRW bn) 312.2 317.6 279.0 280.7 259.9 YoY +13.8% 2Q24 3Q24 4Q24 1Q25 2Q25 ? AI/IT rev includes: AX platform-based including AICC, IoT, Multi/Hybrid Cloud, and Smart Mobility 13

K-IFRS / Consolidated(each subsidiary)  4 Major Subsidiaries • Contents Subsidiaries, revenue +6.0% YoY, driven by increased production, distribution of original contents and subscribers • kt cloud,revenue +23.0% YoY, supported by increased DC usage from global clients and momentum in D&B* *Design & Build operations Revenue of Major Subsidiaries (consolidated) (Unit: KRW bn) 2Q24 1Q25 2Q25 QoQ YoY BC Card 977.7 872.0 909.8 4.3% -6.9% Kt skylife 254.6 242.9 247.2 1.8% -2.9% Content Subsidiaries* 135.4 143.7 143.5 -0.1% 6.0% kt cloud 180.1 249.1 221.5 -11.1% 23.0% kt estate 157.2 137.3 160.4 16.9% 2.0% *kt nasmedia,kt studiogenie(Genie music, Storywiz, and others incl.) *The performance of PlayD was reflected up to 1Q25(disposed on Apr. 3,2025) Subsidiaries’ OP Contribution (Unit: KRW bn) 546.1 288.7 135.1 125.2 89.9 2Q24 3Q24 4Q24 1Q25 2Q25 14

Contents  1 2Q25 Highlights 2 Financial Highlights 3 Business Overview 4 Appendix

1 K-IFRS Income Statement (Unit: KRW bn) Consolidated 2Q24 3Q24 4Q24 1Q25 2Q25 Operating revenue 6,546.4 6,654.6 6,575.6 6,845.1 7,427.4 Service revenue 5,776.6 5,752.0 5,754.7 5,700.4 5,817.8 Sale of goods 769.8 902.7 820.9 1,144.7 1,609.6 Operating expense 6,052.4 6,190.5 7,230.7 6,156.3 6,412.6 Cost of Service 5,178.9 5,111.6 6,256.7 5,114.1 5,129.9 Labor cost 1,213.2 1,118.3 2,189.6 1,121.8 1,119.4 General expense 2,708.3 2,692.6 2,791.2 2,655.8 2,639.7 Cost of service 656.6 699.8 667.5 738.4 755.8 Selling expense 600.8 600.8 608.4 598.0 615.1 Cost of Goods sold 873.5 1,078.9 974.0 1,042.3 1,282.6 Operating income 494.0 464.1 -655.1 688.8 1,014.8 N-OP income (loss) 62.7 45.0 -354.9 23.1 -39.9 N-OP income 325.8 35.8 611.5 199.1 351.4 N-OP expense 260.1 -11.1 969.7 167.9 407.1 Equity Method (G/L) -3.0 -1.9 3.3 -8.2 15.7 Income bf tax 556.7 509.1 -1,010.1 711.8 974.9 Income tax 146.2 125.9 -240.4 145.0 241.6 Net income 410.5 383.2 -769.6 566.8 733.3 NI contribution to KT 393.0 357.3 -655.6 539.8 687.9 EBITDA 1,460.2 1,428.9 318.0 1,657.4 1,990.7 EBITDA Margin 22.3% 21.5% 4.8% 24.2% 26.8% KT Separate 2Q24 3Q24 4Q24 1Q25 2Q25 Operating revenue 4,548.3 4,765.0 4,571.6 4,682.0 4,772.8 Service revenue 4,048.0 4,069.0 3,995.8 4,044.5 4,131.7 Handset revenue 500.3 696.0 575.8 637.5 641.1 Operating expense 4,189.5 4,426.1 5,316.6 4,281.9 4.304.1 Cost of Service 3,696.8 3,688.7 4,713.8 3,620.7 3.677.4 Labor cost 631.3 534.6 1,545.1 460.2 463.0 General expense 1,804.2 1,832.7 1,905.9 1,875.7 1.856.0 Cost of service 630.6 685.6 620.0 647.5 690.6 Selling expense 630.7 635.7 642.8 637.4 667.8 Cost of Devices sold 492.6 737.3 602.8 661.2 626.7 Operating income 358.8 338.9 -745.0 400.1 468.7 N-OP income (loss) 50.3 69.2 -134.5 48.2 -46.2 N-OP income 260.0 32.5 538.7 158.2 317.6 N-OP expense 209.7 -36.7 673.2 110.0 363.9 Income bf tax 409.2 408.0 -879.5 448.3 422.5 Income tax 94.7 98.2 -228.1 82.9 64.5 Net income 314.5 309.8 -651.4 365.4 358.0 EBITDA 1,162.9 1,144.8 70.4 1,210.6 1.281.7 EBITDA Margin 25.6% 24.0% 1.5% 25.9% 26.9% 16

2 K-IFRS Balance Sheet (Unit: KRW bn) Consolidated 2Q24 3Q24 4Q24 1Q25 2Q25 Assets 43,144.4 42,750.4 41,880.0 42,185.6 42,193.3 Current assets 15,175.2 15,197.0 14,251.9 14,458.5 14,385.4 Cash & cash equivalents 3,786.7 3,953.9 3,716.7 3,133.0 3,794.4 Trade & other receivables 4,161.7 4,304.2 3,987.3 4,217.8 3,955.6 Inventories 964.0 903.2 940.2 853.9 443.9 Other current asset 6,262.7 6,035.7 5,607.8 6,253.8 6,191.5—Prepaid_Contract cost 1,233.6 1,236.7 1,233.6 1,325.3 1,304.0—Contract assets 611.1 625.6 577.4 597.9 744.2 Non-current assets 27,969.2 27,553.4 27,628.0 27,727.1 27,808.0 Trade & other rec 398.4 357.0 381.8 336.3 378.3 Tangible assets 14,591.7 14,509.1 14,825.8 14,398.1 14,226.4 Other current assets 12,979.1 12,687.3 12,420.4 12,992.7 13,203.3—Prepaid_Contract cost 471.4 485.2 504.6 462.3 631.5—Contract assets 226.3 225.3 223.4 208.3 146.1 Liabilities 24,162.5 23,564.0 23,883.4 23,847.3 23,316.2 Current liabilities 14,095.2 14,644.5 13,874.7 13,134.6 12,123.5 Trade & other payables 8,052.3 7,712.9 7,394.8 6,952.5 7,077.7 Short-term borrowings 3,595.0 4,358.7 3,904.8 3,649.1 2,934.3 Others 2,447.9 2,572.9 2,575.2 2,533.0 2,111.4 - Contract liabilities 231.2 230.6 226.4 244.1 330.3 Non-current liabilities 10,067.3 8,919.5 10,008.7 10,712.7 11,192.7 Trade & other payables 556.1 573.4 578.4 372.4 383.7 Long-term borrowings 6,555.6 5,409.9 6,615.9 7,520.5 7,815.9 Others 2,955.4 2,936.2 2,814.3 2,819.9 2,933.2—Contract liabilities 43.6 48.7 46.9 48.4 36.6 Equity 18,981.9 19,186.4 17,996.5 18,338.3 18,877.1 Retained earnings 14,452.7 14,675.2 13,779.8 14,197.4 14,739.9 KT Separate 2Q24 3Q24 4Q24 1Q25 2Q25 Assets 30,464.8 29,957.1 29,528.9 29,041.0 29,008.7 Current assets 7,451.7 7,447.7 6,892.6 7,016.3 7,022.2 Cash & cash equi. 1,722.5 1,608.7 1,540.6 1,150.6 1,419.9 Trade & other rec. 3,097.6 3,275.6 2,904.8 3,209.5 2,958.1 Inventories 404.1 264.6 224.7 190.2 166.7 Other current asset 2,227.5 2,298.8 2,222.5 2,465.9 2,477.5—Prepaid_Contract cost 1,312.5 1,318.3 1,308.8 1,405.7 1,389.3—Contract assets 548.6 542.0 521.1 521.4 667.8 Non-current assets 23,013.1 22,509.4 22,636.3 22,024.7 21,986.5 Trade & other rec 321.1 278.2 309.1 241.1 278.9 Tangible assets 11,264.4 11,185.6 11,477.7 11,068.3 10,913.7 Other current assets 10,472.9 10,116.8 9,953.2 9,856.6 9,941.2—Prepaid_Contract cost 453.8 475.3 493.4 454.8 625.6—Contract assets 204.1 201.7 198.2 182.3 116.1 Liabilities 15,166.7 14,513.1 15,108.7 14,409.3 14,165.6 Current liabilities 7,315.1 8,074.9 7,633.2 7,265.4 7,074.7 Trade & other payables 4,694.7 4,421.5 4,585.8 4,258.8 4,459.9 Short-term borrowings 1,789.5 2,860.3 2,434.2 2,263.0 1,895.4 Others 830.8 793.0 613.2 743.6 719.5 - Contract liabilities 206.9 210.5 208.4 217.8 204.8 Non-current liabilities 7,851.6 6,438.2 7,475.5 7,144.0 7,090.9 Trade & other payables 1,063.8 1,010.2 979.4 672.0 666.8 Long-term borrowings 5,675.7 4,290.7 5,437.7 5,417.6 5,184.4 Others 1,112.0 1,137.3 1,058.4 1,054.4 1,239.7—Contract liabilities 26.4 32.9 34.5 37.5 28.0 Equity 15,298.1 15,444.1 14,420.2 14,631.7 14,843.1 Retained earnings 12,404.2 12,579.2 11,717.9 11,965.0 12,156.4 17  K-IFRS / Separate

3 Subscribers K-IFRS / Separate (Unit: Thousands) Wireless Subscribers 2Q 24 3Q 24 4Q 24 1Q 25 2Q 25 QoQ YoY Total 24,904 25,199 26,132 26,445 27,491 4.0% 10.4%—MNO 17,770 17,997 18,950 19,186 19,842 3.4% 11.7%—MVNO 7,134 7,203 7,182 7,259 7,649 5.4% 7.2% 5G Handset1) 10,093 10,251 10,400 10,552 10,866 3.0% 7.7% Churn rate2) 1.0% 1.0% 1.1% 1.0% 1.0% —ARPU (KRW)3) 34,507 34,560 34,567 34,856 35,236 1.1% 2.1% 1) 5G Handset : Retroactively applied from 1Q23 based on the change of subscriber disclosure criteria by the MSIT (excludes 5G 2nd Device and 5G IoT) 2) Churn rate : Based on MNO subscribers (excludes IoT) 3) ARPU = Wireless revenue* / Wireless subscribers** * Wireless revenue(3G, LTE, 5G incl.): Revenue of Voice/Data usage (Interconnection/Subscription fee exc.), VAS, Contract/ Bundled Discounts, and etc. incl. ** Wireless subscribers: Based on MSIT’s guidelines for average billed subscribers in quarter (IoT/M2M exc.) (Unit: Thousands) Fixed Line Subscribers 2Q 24 3Q 24 4Q 24 1Q 25 2Q 25 QoQ YoY Telephony 11,748 11,616 11,475 11,320 11,175 -1.3% -4.9% —PSTN 8,526 8,395 8,264 8,122 7,988 -1.6% -6.3%—VoIP 3,222 3,222 3,211 3,198 3,186 -0.4% -1.1% Broadband 9,899 9,928 9,956 9,984 10,073 0.9% 1.8% IPTV (GTV+GTS) 9,423 9,440 9,449 9,438 9,490 0.6% 0.7% ? Number of IPTV subscribers above differs from MSIT figures that follow the IPTV law —Number of KT pay TV subscribers in 2H 2024 is 8,987,351 (6-month average) 18