KM, Km, or km may stand for:

• Khmer language (ISO 639 alpha-2, km)
• Kilometre/Kilometer (only km in minuscule is the correct representation of kilometer as an SI unit of length)
• Kinemantra Meditation
• Knowledge management, in the field of Library and information science
• Knowledge Machine, the KM knowledge representation language
• Comoros, ISO 3166-1 alpha-2 country code
• Michaelis-Menten constant (K_m) a value relating to enzyme kinetics
• Car designation for the Kamenz
• Car designation for the prefecture of Messenia, it is coded matching with the Latin alphabet, Kalamata
• the IATA code for Air Malta
• KludgeMUSH, the game (kludgemush.com:10321), a Multi-User Simulated Hallucination (MUSH)