O'Brien, Washington was a former community, north of Kent in the Green River Valley of King County in the U.S. state of Washington. It was just north of today's Green River Natural Resources Area, on the right bank of the river. At one time, it had a post office and a school.
The community was named after Terrance O'Brien, the original owner of the town site.
- The Green-Duwamish River: Connecting people with a diverse environment. Duwamish River Cleanup Coalition/TAG. No date, appears to be 2008 or 2009.
- Meany, Edmond S. (1923). Origin of Washington geographic names. Seattle: University of Washington Press. p. 194.