Sumas is a city in Whatcom County, Washington, United States. It had a population of 1,583 as of the 2020 census. Sumas is located adjacent to the Canada–U.S. border and borders the city of Abbotsford, British Columbia. The Sumas–Huntingdon port of entry at the north end of State Route 9 operates 24 hours a day. Sumas shares Nooksack Valley School District with the cities of Nooksack and Everson. It is the northernmost settlement on Washington State Route 9.

Whatcom County is a county located in the northwestern corner of the U.S. state of Washington, bordered by the Lower Mainland of British Columbia to the north, Okanogan County to the east, Skagit County to the south, San Juan County across Rosario Strait to the southwest, and the Strait of Georgia to the west. Its county seat and largest population center is the coastal city of Bellingham, comprising the Bellingham, WA Metropolitan Statistical Area, and as of the 2020 census, the county's population was 226,847.