Castle Espie is a wetland reserve managed by the Wildfowl and Wetlands Trust (WWT) on the banks of Strangford Lough, three miles south of Comber, County Down, Northern Ireland, in the townland of the same name. It is part of the Strangford Lough Ramsar Site. It provides an early wintering site for almost the entire Nearctic population of pale-bellied brent geese. The Castle which gave the reserve its name no longer exists.

The Wildfowl & Wetlands Trust (WWT) is an international wildfowl and wetland conservation charity in the United Kingdom.