Doo and DOO can mean:
- Acronyms
- DOO, driver-only operation, an alternative term for One Person Train Operation
- d.o.o. (društvo s ograničenom odgovornošću), a Private Limited Liability Company in Serbia, Croatia, Bosnia and Herzegovina, Montenegro, Macedonia and Slovenia
- People
- George Thomas Doo (1800-1886), English engraver
- Rulers of the Duala people who lived on the Wouri River estuary of Cameroon:
- Elame a Doo, Duala ruler
- Priso a Doo, Duala ruler
- Other
- Doo (bird), the Rock Pigeon in Scottish English