大岛县（Grand Isle County, Vermont）是美国佛蒙特州西北部的一个县，北邻加拿大，西邻纽约州。面积504平方公里，是全州面积最小的县，而且县内的陆地并不与美国本土相连，全部由尚普兰湖上的岛屿及自加拿大伸出的半岛组成。根据美国2000年人口普查，共有人口6,901人。县治诺斯希洛 (North Hero)。

成立于1802年11月9日。县名来自尚普兰湖上的岛屿。

Grand Isle County is a county located in the state of Vermont, in the United States. As of the 2010 census, the population was 6,970, making it the second-least populous county in Vermont. Its shire town (county seat) is the municipality of North Hero. The county was created in 1802 and organized in 1805.