Stouronisi (Greek: Στουρονήσι) or Styronisi (Στυρονήσι, "island of Styra") is a small island in the Euboean Sea. It is located in the South Euboean Gulf opposite Styra. It is the largest island of a small island complex comprising 7 islets and rocks. The island has an area about 2 km2. Stouronisi has recently become known because of some plans of the Greek government for a development of a high-class summer resort in the island.