Siesta Key is a barrier island off the southwest coast of the U.S. state of Florida, located between Roberts Bay and the Gulf of Mexico. A portion of it lies within the city boundary of Sarasota, but the majority of the key is a census-designated place (CDP) in Sarasota County. Siesta Key is part of the North Port–Bradenton–Sarasota, Florida Metropolitan Statistical Area.

From the 19th century to the early 20th century, Siesta Key was known by a variety of names, including Little Sarasota Key and Sarasota Key. The first attempts to develop the key were by the Siesta Land Company in 1907, consisting of Harry Higel, Captain Louis Roberts, and E. M. Arbogast. The company platted the northern end of the key as Siesta on the Gulf of Mexico as well as dredged bayous and built docks.

Access to Siesta Key was by boat or ferry until the first bridge connecting it to the mainland was completed in 1917. The bridge was replaced in 1927 with the addition of a second bridge located on the southern end of the key. The entire key officially was recognized as Siesta Key by 1952.

On October 9, 2024, Hurricane Milton made landfall as a Category 3 hurricane near Siesta Key.