RUM may refer to:
- the Remington Ultra Magnum family of cartridges
- the United States Department of Defense aerospace vehicle designation#Rocket/missile launch environment for a ship-launched, anti-submarine guided missile
- Real user monitoring, a term used in measuring internet web application performance
- University of Puerto Rico at Mayagüez
- Rigid unit modes, phonon modes in which polyhedra are free to move by translation and/or rotation without distortion
- Republic of the Union of Myanmar, official name of Myanmar