Milton Gate Marsh is a 17.7-hectare (44-acre) biological Site of Special Scientific Interest north-west of Eastbourne in East Sussex.

This site consists of two areas of alluvial wetland in the valleys of the River Cuckmere and one of its tributaries. There is a rich variety of invertebrates, including seventeen nationally scarce species such as the sallow clearwing moth and the beetles Ochthebius exaratus and Stenolphus skrimshiranus.

50°49′52″N 0°10′52″E / 50.831°N 0.181°E / 50.831; 0.181