401 may refer to:

• 401 (number), the natural number following 400 and preceding 402
• A year: 401 BC or AD 401
• Highway 401 (Ontario), a highway that extends across Southern Ontario, Canada.
• 401(k), a type of employer-sponsored retirement plan named after a section of the United States Internal Revenue Code.
• Bristol 401, a car produced by Bristol Cars in the early 1950s
• HTTP 401, a status in the HTTP protocol indicating authentication has failed
• .401 Winchester Self-Loading centerfire rifle cartridge introduced in 1910
• GSX-401FW Stargazer, a prototype mobile suit in the anime Gundam Seed C.E. 73 STARGAZER.
• Area code 401

az:401 (d qiql dirm ) it:401 (disambigua) ht:401 (menm non)