St. Croix Stream is an 18.8-mile-long (30.3 km) river in Aroostook County, Maine. From the outflow of St. Croix Lake (46°18′18″N 68°12′29″W / 46.3050°N 68.2080°W) in St. Croix Township (Township 8, Range 4, WELS), the river runs northwest to the Aroostook River in Masardis. Via the Aroostook River, St. Croix Stream is part of the Saint John River watershed.