Castlebay is the main village and a community council area on the island of Barra in the Outer Hebrides, Scotland. The village is located on the south coast of the island, and overlooks a bay in the Atlantic Ocean dominated by Kisimul Castle, as well as nearby islands such as Vatersay. Castlebay is also within the parish of Barra. The village is located on the A888, which serves as a circular road around Barra. In 1971, it had a population of 307.

Barra is an island in the Outer Hebrides, Scotland, and the second southernmost inhabited island there, after the adjacent island of Vatersay to which it is connected by the Vatersay Causeway. The island is named after Saint Finbarr of Cork.