The Quinault Treaty (also known as the Quinault River Treaty and the Treaty of Olympia) was a treaty agreement between the United States and the Native American Quinault and Quileute tribes located in the western Olympic Peninsula north of Grays Harbor, in the recently formed Washington Territory. The treaty was signed on 1 July 1855, at the Quinault River, and on 25 January 1856 at Olympia, the territorial capital. It was ratified by Congress on 8 March 1859, and proclaimed law on April 11, 1859.
Signatories included Isaac Stevens, superintendent of Indian affairs and governor of Washington Territory, and representatives of the Quinault and Quileute, as well as the Hoh tribe, which was considered a subset of the Quileutes. The Quinault Indian Reservation was established under the terms of the treaty. Indian signatories included the Quinault Head Chief Taholah and Sub-chiefs Wah-kee-nah, Yer-ay-let'l, and Kne-she-guartsh, the Quileute Head Chief How-yat'l and Sub-chiefs Kal-lape, Tah-ah-ha-wht'l, along with other tribal delegates.
The Quinault Treaty was one of the last of several signed during Washington Territory's first decade. Acquiring land cession from the Native Americans was one of Isaac Stevens' primary goals as the first governor of the territory. Other similar cession treaties Stevens negotiated in the 1850s include the Treaty of Medicine Creek, Treaty of Hellgate, Treaty of Neah Bay, Treaty of Point Elliott, and the Point No Point Treaty.