Rushley Island is a small uninhabited island in Essex, England. It is the smallest of six islands comprising an archipelago in Essex, and is privately owned. A seawall was first constructed in the 1780s by John Harriott, and the island has been the object of farming activities since then.

The local racehorse trainer and one-time Rushley Island owner, Frank Threadgold, once bred a horse which he named after the island.