KTB can mean:
- Cretaceous-Paleogene boundary also known as Cretaceous-Tertiary boundary
- Khatib MRT station (station abbreviation KTB), Yishun, Singapore
- Krung Thai Bank, state-owned Thai commercial bank
- KTB ML(military logistics) Vietnam. since 1981 (Change to a start-up investment company in 1986)
- ktb, ISO 639-3 code for the Kambaata language
- KTB, IATA code for Thorne Bay seaplane base
- K-T-B, triconsonantal root of a number of Semitic words
- Kontinentales Tiefbohrprogramm der Bundesrepublik Deutschland (German Continental Deep Drilling Program), a German scientific project
- KTB, stock symbol for Kontoor Brands