IRN may refer to:

• Input-referred noise
• Independent Radio News, a news service to commercial radio stations in the United Kingdom
• Independent Radio News (New Zealand), not affiliated with the United Kingdom company above
• International Rivers Network, a non-profit environmental organization based in California, United States
• Imperial Russian Navy, the navy of the Russian Empire
• Iran (ISO 3166-1 alpha-3 country code)
• Indian-ringnecked parakeet (abbreviated IRN), the subspecies Psittacula krameri manillensis of the rose-ringed parakeet
• Islamic Council Norway, Islamsk Råd Norge
• Italian Royal Navy, the navy of the Kingdom of Italy