MWO may refer to:
- Master warrant officer, a military rank in the Canadian Forces
- Max Watts Out, a non-standard unit of power rating, aka Units Watts Out (UWO)
- MechWarrior Online, a vehicular combat video game
- Media Whores Online, a defunct left-wing blog
- Meyer–Womble Observatory, an astronomical observatory near Mount Evans, Colorado, USA
- Middletown Regional Airport, (IATA: MWO, ICAO: KMWO, FAA LID: MWO)
- Militaire Willems-Orde (Military Order of William), a Netherlands chivalric order
- Mount Washington Observatory, a scientific and educational institution with a weather observation station at Mount Washington in New Hampshire
- Mount Wilson Observatory, an astronomical observatory in Los Angeles County, California, USA