Mouser may refer to:
- A domestic cat used for hunting rodents.
- Chief Mouser to the Cabinet Office, the official resident cat of the Prime Minister of the United Kingdom.
- Mouser Electronics, an electronic component retailer.
- Mouser, 1983 computer game from IBM about a cat who pushes blocks on mice.
- A type of robot from the Teenage Mutant Ninja Turtles series created by Baxter Stockman.
- A boss in the video game Super Mario Bros. 2 and recurring villain for cartoon segments of The Super Mario Bros. Super Show!.
- A name for a fan of the band Modest Mouse.