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 November 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 3Q25 EarningsRelease 2025.11. | Investor Relations

2 Disclaimer This presentation has been prepared by KT Corp.(the “Company”) inaccordance 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

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

4 3Q25 Highlights 1 7,126.7bn(YoY +7.1%) 538.2bn(YoY +16.0%) 5,109.0bn(YoY +7.2%) 340.9bn(YoY +0.6%) OP increased,driven by real estate PJT*, CT and group portfolio growth Financials Operating Profit Revenue Cons. Sep. Operating Profit Revenue (Unit: KRW) * Gwangjin-gu Lotte Eastpole Apartment ** Operating profit up 26.2% YoY(consolidated) / 14.6% YoY(separate), excluding one-off wage negotiation cost(KRW 47.5bn.) Hacking incidents Strengthening AX Biz. Launched multi-AI models —KT developed Mi:dm2.0/MS collaborationSOTA K/ Open-source Llama K New products based on MS partnership —GPUaaSSep.10, Secure Public Cloud 4Q Opened ‘KTInnovationHub’ (Oct.20) —Tailored AX consulting by KT-MS experts Shareholder return Customer compensation measures —USIM replacement for total KT subscribers—368 subs. (affected by unauthorized micropayments) : Full reimbursement (Total KRW 240mn.)—22,227 subs. (affected by illegal base station connections) : Compensation package (incl. cancellation fee waivers) Measures to prevent recurrence —Strengthened micro base station and mgmt. system—Real-time fraud abnormal payments monitoring system—Abnormal access/device-change blocking system FDS -Investment of KRW 1tn. over five years for security 3Q25 dividend (Payment‘25.11.20) —DPSKRW600 (‘25 YTDKRW 1,800)

5 AICT Company AICT Transformation 1-2 FY2028 Financial Target and Action Plans FY2028 Financial Target and Action Plans AICT Transformation AI/IT Rev. Share Up 3xof 2023 Secure Profitability Consolidated OP Margin 9% Asset Optimization Non-Core Asset Liquidation Additional Shareholder Return KRW 1tr. Share buyback Attain top-AI/Cloud capabilities (by global big tech partnership) Enhance OP through streamlining low-profit biz. Liquidate non-core assets and idle real estate Enhance capital efficiency through additional returns Progress [2024~2025.3Q] Strengthened AX capability with strategic partnership (AI model SOTA K , Palantir partnership) Improved Business and cost structure (Low-margin 39 biz., KRW 50bn.) Monetized non-core assets (Profit KRW82.4bn./CashKRW275.7bn) ‘25 Share buyback KRW 250bn. (Cancellation will be executed in consideration of foreign ownership limits) Strategy    Integrate AI into core biz.Telco, Media, NW, IT, accelerate growth of B2B AX and revamp mgmt. structure

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

7 Income Statement 1 (Unit: KRW bn) 1) OP Margin1 = Operating Income/Service Revenue3Q24 2Q25 3Q25 QoQ YoY Operating Revenue 6,654.6 7,427.4 7,126.7 -4.0% 7.1% Service Revenue 5,752.0 5,817.8 5,920.8 1.8% 2.9% Sale of goods 902.7 1,609.6 1,205.9 -25.1% 33.6% Operating Expense 6,190.5 6,412.6 6,588.6 2.7% 6.4% Operating Income 464.1 1,014.8 538.2 -47.0% 16.0% Margin 7.0% 13.7% 7.6% -6.1%p 0.6%p Margin1 8.1% 17.4% 9.1% -8.4%p 1.0%p Non-op. Income/Loss 45.0 -39.9 55.3 Turned to profit 22.9% Income before taxes 509.1 974.9 593.4 -39.1% 16.6% Net Income 383.2 733.3 445.3 -39.3% 16.2% Margin 5.8% 9.9% 6.2% -3.6%p 0.5%p EBITDA 1,428.9 1,990.7 1,503.9 -24.5% 5.2% Margin 21.5% 26.8% 21.1% -5.7%p -0.4%p Revenue +7.1% YoY driven by growth in telecom, real estate, and cloud/DC business OP +16.0% reflecting KT Group-wide efforts for profitability and gains from real estate development 

OP. expenses +6.4% YoY, led by higher cost of service, goods sold(COGS) and selling expense 8 K-IFRS / Consolidated Operating Expenses 2 (Unit: KRW bn) [Selling Expense (KT Separate)] (Unit: KRW bn) OP. expenses +6.4% YoY, led by higher cost of service,goods sold(COGS) and selling expense K-IFRS / Consolidated2Q24 1Q25 2Q25 QoQ YoY Operating Expenses 6,190.5 6,412.6 6,588.6 2.7% 6.4% Labor Cost 1,118.3 1,119.4 1,167.6 4.3% 4.4% General Expense 2,692.6 2,639.7 2,725.9 3.3% 1.2%—Depreciation 964.8 975.9 965.7 -1.0% 0.1% Cost of Service 699.7 755.8 778.5 3.0% 11.3% Selling Expense 600.8 615.1 632.6 2.8% 5.3% Cost of Goods sold 1,079.0 1,282.6 1,283.9 0.1% 19.0% [Selling Expense (KT Separate)] 3Q25 2Q25 3Q24 QoQ YoY Selling Expense 623.9 655.8 669.8 2.1% 7.4% (Unit: KRW bn)

9 Balance Sheet 3 Net Debt/equity ratio -2.3%p QoQ due to lower borrowings (Unit: KRW bn) K-IFRS / Consolidated Sep. 30, 2024 Jun. 30, 2025 Sep. 30, 2025 QoQ YoY Assets 42,750.4 42,193.3 43,012.8 1.9% 0.6% Cash & Cash equivalents 3,953.9 3,794.4 3,890.3 2.5% -1.6% Liabilities 23,564.0 23,316.2 23,752.8 1.9% 0.8% Borrowings 9,768.6 10,750.2 10,532.3 -2.0% 7.8% Equity 19,186.4 18,877.1 19,259.9 2.0% 0.4% Capital Stock 1,564.5 1,564.5 1,564.5 — Net Debt 5,814.7 6,955.8 6,642.0 -4.5% 14.2% Debt / Equity 122.8% 123.5% 123.3% -0.2%p 0.5%p Net Debt / Equity 30.3% 36.8% 34.5% -2.3%p 4.2%p K-IFRS / Consolidated

10 CAPEX 4 K-IFRS / Separate and major subsidiaries Major Subsidiaries’ CAPEX Includes Finance, Media, Cloud/DC, Real Estate, etc. KT SeparateCAPEX Access network, Backbone Network, B2B and etc. K-IFRS / Separate and major subsidiaries (Unit: KRW bn) 3Q25 Total CAPEX Execution: KRW 1,329.5bn (KT Separate), KRW 634.2bn(Major Subsidiaries) 3,534 3,319 3,124 1,9642,721 2,412 2,300 1,330 813 907 824 634 2022 2023 2024 3Q25(Cum.) KT Major Subsidiaries Major Subsidiaries’ CAPEX Includes Finance, Media, Cloud/DC, Real Estate, etc. KT Separate CAPEX Access network, Backbone Network, B2B and etc.

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

12 KT—Wireless Wireless service revenue +4.7% YoY with increased 5G subs (5G penetration 80.7%) Continued efforts to differentiate products, distribution and pricing 1 (Unit: KRW bn)3Q24 2Q25 3Q25 QoQ YoY Wireless 1,740.4 1,781.7 1,809.6 1.6% 4.0% WirelessService 1,656.5 1,704.8 1,733.6 1.7% 4.7% Interconnection 83.9 76.9 76.0 -1.1% -9.4% Handset (5G) Handset (exc. 5g) 2nd devise & lot MNVO 12

13 KT—Fixed Line Broadband revenue +2.3% YoY, due to increase in GiGA subscribers and value-added services Media rev. up +3.1% YoY, backed by IPTV subscriber net adds and premium plans uptake K-IFRS / Separate 2 (Unit: Thousands) BroadbandSubscribers (Unit: Thousands) IPTVSubscribers3Q24 2Q25 3Q25 QoQ YoY Fixed Line 1,312.6 1,334.5 1,331.9 -0.2% 1.5% Broadband 622.2 631.4 636.7 0.8% 2.3% Media 518.2 526.9 534.4 1.4% 3.1% Home Telephony 172.2 176.2 160.9 -8.7% -6.6% 

14 KT—B2B Services 3 K-IFRS / Separate (Unit: KRW bn) Corp.Broadband/Data Revenue Revenue of AI/IT ? AI/IT rev includes: AX platform-based including AICC, IoT, Multi/Hybrid Cloud, and Smart Mobility3Q24 2Q25 3Q25 QoQ YoY B2B Service 926.4 922.7 932.7 1.1% 0.7% B2B services rev. +0.7% YoY, driven by growth in corporate telecom businesses,    despite continued streamlining of low-margin businesses Corp. Broadband/Data rev includes: Leased line, Kornet, VPN, Global data AI/IT rev includes: AX platform-based including AICC, IoT, Multi/Hybrid Cloud, and Smart Mobility

15 Major Subsidiaries 4 kt cloud rev. +20.3% YoY, due to increased usage of DC from global clients and public AI Cloud ktestaterev+23.9%YoY,supported by growth in hotel business and new development* project *Daejeon HR Center (Unit: KRW bn) *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) 15 Revenue of Major Subsidiaries (consolidated)3Q24 2Q25 3Q25 QoQ YoY BCCard 931.4 909.8 918.3 0.9% -1.4% kt skylife 256.9 247.2 246.9 -0.1% -3.9% Content Subsidiaries* 156.2 143.5 153.3 6.8% -1.8% kt cloud 207.0 221.5 249.0 12.4% 20.3% kt estate 150.8 160.4 186.9 16.5% 23.9% 

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

1 K-IFRS Income Statement (Unit: KRW bn) Consolidated 3Q24 4Q24 1Q25 2Q25 3Q25 KT Separate 3Q24 4Q24 1Q25 2Q25 3Q25    Operating revenue 6,654.6 6,575.6 6,845.1 7,427.4 7,126.7 Operating revenue 4,765.0 4,571.6 4,682.0 4,772.8 5,109.0    Service revenue 5,752.0 5,754.7 5,700.4 5,817.8 5,920.8 Service revenue 4,069.0 3,995.8 4,044.5 4,131.7 4,179.9 Sale of goods 902.7 820.9 1,144.7 1,609.6 1,205.9 Handset revenue 696.0 575.8 637.5 641.1 929.1    Operating expense 6,190.5 7,230.7 6,156.3 6,412.6 6,588.6 Operating expense 4,426.1 5,316.6 4,281.9 4.304.1 4,768.1    Cost of Service 5,111.5 6,256.7 5,114.1 5,129.9 5,304.6 Cost of Service 3,688.7 4,713.8 3,620.7 3.677.4 3,837.8 Labor cost 1,118.3 2,189.6 1,121.8 1,119.4 1,167.6 Labor cost    534.6 1,545.1 460.2 463.0 492.8 General expense 2,692.6 2,791.2 2,655.8 2,639.7 2,725.9 General expense 1,832.7 1,905.9 1,875.7 1.856.0 1,956.7 Cost of service 699.7 667.5 738.4 755.8 778.5 Cost of service    685.6 620.0 647.5 690.6 707.4 Selling expense 600.8 608.4 598.0 615.1 632.6 Selling expense    635.7 642.8 637.4 667.8 680.9 Cost of Goods sold 1,079.0 974.0 1,042.3 1,282.6 1,283.9 Cost of Devices sold    737.3 602.8 661.2 626.7 930.3    Operating income 464.1 -655.1 688.8 1,014.8 538.2 Operating income    338.9 -745.0 400.1 468.7 340.9    N-OP income (loss) 45.0 -354.9 23.1 -39.9 55.3 N-OP income (loss)    69.2 -134.5 48.2 -46.2 39.3 N-OP income 35.8 611.5 199.1 351.4 132.7 N-OP income    32.5 538.7 158.2 317.6 72.6 N-OP expense -11.1 969.7 167.9 407.1 74.2 N-OP expense -36.7 673.2 110.0 363.9 33.2 Equity Method (G/L) -1.9 3.3 -8.2 15.7 -3.3    Income bf tax 509.1 -1,010.1 711.8 974.9 593.4 Income bf tax    408.0 -879.5 448.3 422.5 380.2 Income tax 125.9 -240.4 145.0 241.6 148.2 Income tax    98.2 -228.1 82.9 64.5 90.5    Net income 383.2 -769.6 566.8 733.3 445.3 Net income    309.8 -651.4 365.4 358.0 289.7 NI contribution to KT 357.3 -655.6 539.8 687.9 391.5    EBITDA 1,428.9 318.0 1,657.4 1,990.7 1,503.9 EBITDA EBITDA Margin 1,144.8 70.4 1,210.6 1.281.7 1,153.8 EBITDA Margin 21.5% 4.8% 24.2% 26.8% 21.1% 24.0% 1.5% 25.9% 26.9% 22.6% 

K-IFRS Balance Sheet (Unit: KRW bn) 18 Consolidated 3Q24 4Q24 1Q25 2Q25 3Q25 KT Separate 3Q24 4Q24 1Q25 2Q25 3Q25          Assets 42,750.4 41,880.0 42,185.6 42,193.3 43,012.8 Assets    29,957.1 29,528.9 29,041.0 29,008.7 29,049.2          Current assets 15,197.0 14,251.9 14,458.5 14,385.4 15,123.6 Current assets    7,447.7 6,892.6 7,016.3 7,022.2 7,127.8 Cash & cash equivalents 3,953.9 3,716.7 3,133.0 3,794.4 3,890.3 Cash & cash equi.    1,608.7 1,540.6 1,150.6 1,419.9 1,095.5 Trade & other receivables 4,304.2 3,987.3 4,217.8 3,955.6 4,215.7 Trade & other rec.    3,275.6 2,904.8 3,209.5 2,958.1 3,186.5 Inventories 903.2 940.2 853.9 443.9 443.8 Inventories    264.6 224.7 190.2 166.7 155.2 Other current asset 6,035.7 5,607.8 6,253.8 6,191.5 6,573.7 Other current asset    2,298.8 2,222.5 2,465.9 2,477.5 2,690.7 —Prepaid_Contract cost 1,236.7 1,233.6 1,325.3 1,304.0 1,450.7 —Prepaid_Contract cost    1,318.3 1,308.8 1,405.7 1,389.3 1,549.9 —Contract assets 625.6 577.4 597.9 744.2 805.2 —Contract assets    542.0 521.1 521.4 667.8 707.8    Non-current assets 27,553.4 27,628.0 27,727.1 27,808.0 27,889.2 Non-current assets    22,509.4 22,636.3 22,024.7 21,986.5 21,921.4 Trade & other rec 357.0 381.8 336.3 378.3 422.1 Trade & other rec    278.2 309.1 241.1 278.9 319.9 Tangible assets 14,509.1 14,825.8 14,398.1 14,226.4 14,121.1 Tangible assets    11,185.6 11,477.7 11,068.3 10,913.7 10,748.7 Other current assets 12,687.3 12,420.4 12,992.7 13,203.3 13,346.0 Other current assets    10,116.8 9,953.2 9,856.6 9,941.2 10,028.4 —Prepaid_Contract cost 485.2 504.6 462.3 631.5 629.2 —Prepaid_Contract cost    475.3 493.4 454.8 625.6 624.1 —Contract assets 225.3 223.4 208.3 146.1 173.2 —Contract assets    201.7 198.2 182.3 116.1 140.1    Liabilities 23,564.0 23,883.4 23,847.3 23,316.2 23,752.8 Liabilities    14,513.1 15,108.7 14,409.3 14,165.6 13,986.4    Current liabilities 14,644.5 13,874.7 13,134.6 12,123.5 12,223.6 Current liabilities    8,074.9 7,633.2 7,265.4 7,074.7 6,539.8 Trade & other payables 7,712.9 7,394.8 6,952.5 7,077.7 7,770.5 Trade & other payables    4,421.5 4,585.8 4,258.8 4,459.9 4,545.4 Short-term borrowings 4,358.7 3,904.8 3,649.1 2,934.3 2,454.1 Short-term borrowings    2,860.3 2,434.2 2,263.0 1,895.4 1,310.4 Others 2,572.9 2,575.2 2,533.0 2,111.4 1,999.0 Others    793.0 613.2 743.6 719.5 684.1 —Contract liabilities 230.6 226.4 244.1 330.3 228.1 —Contract liabilities    210.5 208.4 217.8 204.8 198.3    Non-current liabilities 8,919.5 10,008.7 10,712.7 11,192.7 11,529.2 Non-current liabilities    6,438.2 7,475.5 7,144.0 7,090.9 7,446.6 Trade & other payables 573.4 578.4 372.4 383.7 386.6 Trade & other payables    1,010.2 979.4 672.0 666.8 649.8 Long-term borrowings 5,409.9 6,615.9 7,520.5 7,815.9 8,078.2 Long-term borrowings    4,290.7 5,437.7 5,417.6 5,184.4 5,499.5 Others 2,936.2 2,814.3 2,819.9 2,993.2 3,064.4 Others    1,137.3 1,058.4 1,054.4 1,239.7 1,297.2 —Contract liabilities 48.7 46.9 48.4 36.6 33.4 —Contract liabilities    32.9 34.5 37.5 28.0 27.3    Equity 19,186.4 17,996.5 18,338.3 18,877.1 19,259.9 Equity    15,444.1 14,420.2 14,631.7 14,843.1 15,062.8 Retained earnings 14,675.2 13,779.8 14,197.4 14,739.9 14,986.2 Retained earnings    12,579.2 11,717.9 11,965.0 12,156.4 12,301.6    

3 Subscribers K-IFRS / Separate (Unit: Thousands) Wireless Subscribers 3Q 24 4Q 24 1Q 25 2Q 25 3Q 25 QoQ YoY Total 25,199 26,132 26,445 27,491 28,328 3.0% 12.4% —MNO 17,997 18,950 19,186 19,842 20,271 2.2% 12.6% —MVNO 7,203 7,182 7,259 7,649 8,057 5.3% 11.9% 5G Handset1) 10,251 10,400 10,552 10,866 11,048 1.7% 7.8% Churn rate2) 1.0% 1.1% 1.0% 1.0% 1.1% 0.1%p 0.1%p ARPU (KRW)3)    34,560 34,567 34,856 35,236 35,295 0.2% 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.) Fixed Line Subscribers 3Q 24 4Q 24 1Q 25 2Q 25 3Q 25 QoQ YoY Telephony 11,616 11,475 11,320 11,175 11,039 -1.2% -5.0% —PSTN 8,395 8,264 8,122 7,988 7,851 -1.7% -6.5% —VoIP 3,222 3,211 3,198 3,186 3,188 0.0% -1.1% Broadband 9,928 9,956 9,984 10,073 10,135 0.6% 2.1% IPTV (GTV+GTS) 9,440 9,449 9,438 9,490 9,520 0.3% 0.8% ?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) 19

KT