Vieques ( : [ˈbjekes]; : [viːˈeɪkeɪz] or [-kɛz]), in full Isla de Vieques, is an island-municipality of Puerto Rico in the northeastern Caribbean. Although Puerto Rico is a U.S. Commonwealth, Vieques, like the rest of Puerto Rico, retains strong Spanish influences from 400 years of Spanish ownership.

Vieques lies about to the east of the Puerto Rican mainland, and measures approximately long by wide. The two main towns of Vieques are Isabel Segunda (sometimes written "Isabel II"), the administrative center located on the northern side of the island, and Esperanza, located on the southern side. At peak, the population of Vieques is around 10,000.

The island's name is a Spanish spelling of a Native American word said to mean "small island". It also has the nickname "Isla Nena", usually translated from the Spanish as "Little Girl Island", as a reference to its being perceived as Puerto Rico's little sister island. During the colonial period the British name was "Crab Island".

Vieques is best known internationally as the site of a series of protests against the US Navy's use of the island as a bombing range and weapons testing ground, which eventually led to the Navy's departure in 2003.