IJN may refer to:

• International Justice Network, a human rights organization
• Imperial Japanese Navy, the navy of Japan from 1868 until it was dissolved in 1945
• IJN, a 1978 wargame about naval combat in the Pacific during World War II
• Institut Jean Nicod, a French interdisciplinary research center
• Institut Jantung Negara, National Heart Institute of Malaysia
• Intermountain Jewish News, an international weekly newspaper publication located in Denver, Colorado
• Kalabari language (ISO 639-3 code ijn)