Washington, officially the State of Washington, is a state in the Pacific Northwest region of the United States. It is often referred to as Washington state to distinguish it from the national capital, both named for George Washington. Washington borders the Pacific Ocean to the west, Oregon to the south, Idaho to the east, and the Canadian province of British Columbia to the north. The state was formed from the western part of the Washington Territory, which was ceded by the British Empire in the Oregon Treaty of 1846. It was admitted to the Union as the 42nd state in 1889. Olympia is the state capital, and the most populous city is Seattle.

The Northwestern United States, also known as the American Northwest or simply the Northwest, is an informal geographic region of the United States. The region consistently includes the states of Oregon, Washington, Idaho, Montana and Wyoming. Some sources include Southeast Alaska in the Northwest. The related but distinct term "Pacific Northwest" generally excludes areas from the Rockies eastward, whereas the term "Inland Northwest" excludes areas west of the Cascades.