Ingrebourne Marshes are a 74.8 hectare biological Site of Special Scientific Interest in Hornchurch in the London Borough of Havering.

[3][4] The Marshes run along both sides of the river, the northern portion next to Hornchurch Country Park and stretching south to Rainham.

Invertebrates include sixteen nationally scarce fly, beetle dragonfly and cricket species.

There are two nationally rare Red Data Book species, the hoverfly Anasimyia interpuncta and the scarce emerald damselfly Lestes dryas.

[1] Havering Council has raised the water level and reintroduced grazing to protect the wetland.