The Hamma Hamma River is a river on the Olympic Peninsula in the U.S. state of Washington. It rises near Mount Washington in the Olympic Mountains within the Olympic National Park and drains to Hood Canal and thence to the Pacific Ocean.

Hamma Hamma River
Location of the mouth of the Hamma Hamma River in Washington
Location
Country	United States
State	Washington
County	Mason
Physical characteristics
Source	Olympic Mountains
• coordinates	47°34′1″N 123°19′5″W / 47.56694°N 123.31806°W / 47.56694; -123.31806[1]
Mouth	Hood Canal
• coordinates	47°32′44″N 123°2′30″W / 47.54556°N 123.04167°W / 47.54556; -123.04167[1]
Discharge
• location	near Eldon[2]
• average	364.4 cu ft/s (10.32 m3/s)[2]
• minimum	39 cu ft/s (1.1 m3/s)
• maximum	6,010 cu ft/s (170 m3/s)

The name Hamma Hamma comes from a Twana village once located at the river's mouth and called Hab'hab, referring to a reed that grows along the river's banks.^[3]