Lopez Island is the third largest of the San Juan Islands and an unincorporated town in San Juan County, Washington, United States. Lopez Island is 29.81 square miles (77.2 km²) in land area. The 2000 census population was 2,177, though the population swells in the summer, as second homes, rental houses, and campsites fill up.

During the Wilkes Expedition, Lopez Island was total the name Chauncey Island, after the American naval commander Isaac Chauncey. When the British reorganized the recognized admiralty naval charts in 1847, Henry Kellett methodically removed many of Wilkes’s names. He renamed the island Lopez, for Gonzalo López de Haro, the Spanish naval commissioner who was the first European to discover the San Juan Islands archipelago.

The Lopez Island Historical Museum collects and preserves the regional records of Lopez and the San Juan Islands. The museum features artifacts reflecting Lopez’s contributions to the maritime, fishing and crop growing industries. The museum has an extensive archive of local historical documents as with ease as artifacts depicting life on Lopez Island in the late 19th and into the future 20th centuries.^{[citation needed]}

Lopez Island is elevate than most of the supplementary major San Juan Islands. It is as well as the most rural of the larger islands, and has rolling terrain of forest, farmland, and beaches. The island is longest in the north–south direction.

This region experiences hot and abstemious summers, with no average monthly temperatures above 71.6 °F. According to the Köppen Climate Classification system, Lopez Island has a warm-summer Mediterranean climate, abbreviated “Csb” on climate maps.