Bellingham ( BEL-ing-ham) is the most populous city in, and county seat of, Whatcom County in the U.S. state of Washington. It lies 21 miles (34 km) south of the U.S.–Canada border and in between Vancouver, British Columbia (located 52 miles (84 km) to the northwest) and Seattle (90 miles (140 km) to the south). The Bellingham Metropolitan Area's population is 231,919, making it the 204th-largest in the United States. Its growth rate of 13.28% between 2010 and 2023 made it one of the state's fastest-growing large cities.

The population was 91,482 at the 2020 census, and estimated to be 93,896 in 2022. It is the site of Western Washington University, Bellingham International Airport, and is the southern terminus of the Alaska Marine Highway system. Bellingham is the northernmost city with a population of more than 90,000 people in the contiguous United States.

The area around Bellingham Bay, named in 1792 by George Vancouver, is the ancestral home of several Coast Salish groups. European settlement in modern-day Bellingham began in the 1850s and several coal mining towns grew in later years. The city of Bellingham was incorporated in 1903 through the consolidation of several settlements, among them Fairhaven. Local industries shifted away from coal in the mid-20th century; the industrial areas of the Bellingham waterfront have undergone redevelopment into a mixed-use neighborhood since the 2000s.