Whatcom County /ˈhwɒtkəm/ is a county located in the U.S. state of Washington.

As of the 2016 census, the population was 216,800. The county seat and largest city is Bellingham. The county was created out of Island County by the Washington Territorial Legislature on March 9, 1854, and originally included present day San Juan County and Skagit County. Its name ultimately derives from the Lummi word Xwotʼqom, meaning "noisy water."