Sinjido () is an island located off the coast of South Jeolla Province, South Korea. It covers an area of 30.99 km<sup>2</sup>, and has a coast line which is 48.0 km long. It features several peaks: Sang-san (324 m), Nohak-bong (225 m), Beom-san (151 m), and Giseon-bong (141 m). A bridge connecting Wando County and Sinjido was completed in 2005, and another, connecting Sinjido to Gogeum, was completed in 2017.
In 2021, the population was 3,312.