Brown Island is a small, private island in Friday Harbor on San Juan Island, San Juan County, Washington, United States. It lies just offshore to the east-northeast of the town of Friday Harbor, Washington. The island has a land area of approximately and on January 1, 2008, it had a resident full-time population of 10 people.
Brown Island was named by the Wilkes Expedition in 1841 for the party's navigational instrument repairman, John G. Brown.