Whidbey Island (historical spelling Whidby) is the largest of nine islands located in Island County, Washington, in the United States. Whidbey is about 30 miles (48 km) north of Seattle, and lies between the Olympic Peninsula and the I-5 corridor of western Washington. The island forms the northern boundary of Puget Sound. It is home to Naval Air Station Whidbey Island.
Whidbey Island is approximately 35 miles (56 km) long (from the extreme north to extreme south, and 1.5 to 12 miles (2.4 to 19.3 km) wide, with 168.67 square miles (436.9 km2), making it the 40th largest island in the United States. It is ranked as the fourth longest and fourth largest island in the contiguous United States, behind Padre Island, Texas (the world’s longest barrier island); Long Island (a fact disputed by residents); and Isle Royale, Michigan. In the state of Washington, it is the largest island, followed by Orcas Island.