安格尔西岛(英语：Isle of Anglesey，威尔士语：Ynys Môn)，是英国威尔士西北部一岛屿，隔梅奈海峡与大不列颠岛相邻，面积715平方公里，人口68900人（2005年），语言主要是威尔士语。安格尔西岛是威尔士第一大岛，也是英国第五大岛。

Anglesey or Ynys Môn (Welsh:Ynys Môn [ˈənɨs ˈmoːn]) is an island off the north-west coast of Wales. With an area of 276 square miles (715 km), Anglesey is by far the largest island of Wales and the fifth-largest island surrounding Great Britain (and the largest outside Scotland). Anglesey is also the largest island in the Irish Sea by area, and the second most populous island in the Irish Sea (after the Isle of Man). The population at the 2011 census was 69,751. Two bridges span the Menai Strait, connecting the island to the mainland: the Menai Suspension Bridge, designed by Thomas Telford in 1826, and the Britannia Bridge.