盖尔赛岛是苏格兰的岛屿，位于大西洋海域，属于奥克尼群岛的一部分，长3.2公里、宽1.6公里，面积2.4平方公里，最高点海拔高度102米，2001年人口仅3人。

Gairsay (Old Norse: Gáreksey) is a small island in Orkney, Scotland, located in the parish of Rendall, 1.5 miles (2.4 km) off the coast, astride one of the approaches to the bays of Firth and Kirkwall. It is about 2 miles (3.2 km) long and 1 mile (1.6 km) wide and includes one conical hill and a small harbour called Millburn Bay, which is sheltered by the peninsula known as the Hen of Gairsay.