Ray Mill Island is an island in the River Thames in England at Boulter's Lock near Maidenhead, Berkshire.
The island is now a park administered by the Royal Borough of Windsor and Maidenhead. It is named after the Ray family who once had a flour mill here. The mill was constructed in 1726 on the site of a previous mill, and continued to produce flour until the 1920s.
Boulter's weir runs from the top end of the island across to the Taplow bank. A kayak flume has been built adjacent to the weir on the island.
| Next island upstream | River Thames | Next island downstream |
| Boulter's Island | Ray Mill Island | Grass Eyot |