Monkey Island is an island in the River Thames in England, on the reach above Boveney Lock. Its nearest village is Bray, Berkshire. The dominant building on the island is a small hotel since the late 19th century. The reach on which it sits is a main reach in boat hiring and tour boating, between Windsor and Maidenhead. The island and the reach have been a tour destination since Georgian times – particularly so after its purchase by the Duke of Marlborough of 1738 who in nameplay put colourful statues of monkeys in his various gardens for visitors to discover. In one of his two small buildings on the island some of these remain.

This article lists the islands in the River Thames, or at the mouth of a tributary, in England. It excludes human-made islands built as part of the building of forty-five two-gate locks which each accompany a weir, and islets subordinate to and forming part of the overall shape of another. The suffix -ey is common across England and Scotland and cognate with ait and meaning island, a term – as ait or eyot – unusually well-preserved on the Thames. A small minority of list entries are referred to as Island, Ait or Eyot and are vestiges, separated by a depression in the land or high-water-level gully.