Saint Croix is an island in the Caribbean Sea, and a county and constituent district of the United States Virgin Islands (USVI), an unincorporated territory of the United States.

St. Croix is the largest of the islands in the territory. However, the territory's capital, Charlotte Amalie, is located on Saint Thomas. As of the 2010 United States Census, St. Croix's population was 50,601.The island's highest point is Mount Eagle, at 355 metres (1,165 ft). St. Croix's nickname is "Twin City", for its two towns, Frederiksted on the western end and Christiansted on the northeast part of the island.