Big Branch Marsh National Wildlife Refuge, National Wildlife Refuge in St. Tammany Parish, Louisiana.

Big Branch Marsh National Wildlife Refuge covers 15,000 acres (6,100 ha) of pine flatwoods, oak ridges and coastal marsh along Lake Pontchartrain in St. Tammany Parish, Louisiana. Its habitat zones run from the sandy beach fringing the lake through brackish marsh and a wiregrass and spike rush zone to upland pine flatwoods and bottomland hardwood hammocks.

The refuge was established in 1994 to protect natural coastline sections along Lake Pontchartrain. Its creation helped preserve habitats as surrounding communities experienced rapid residential and urban expansion.

The refuge's name comes from Big Branch, a waterway within the Saint Tammany Parish site about 8.6 km west of Slidell. Since 2008, discarded Christmas trees have been wired into fences in the Goose Point and Point Platte marsh areas, where they slow wave action and trap sediment.

The Boy Scout Road Trail boardwalk, destroyed by Hurricane Katrina, was rebuilt in early 2007 and gives access over the marsh. The refuge lies about 8.6 km west of Slidell in Saint Tammany Parish, with Bayou Paquet roughly 1.2 km to the east. Sections of marsh were restored in 2008 at Goose Point and Point Platte.

The refuge's Christmas tree fences are discarded evergreens staked into the marsh to slow wave action, trap sediment and fight erosion; they were installed in sections of the marsh after the 2008 restoration work at Goose Point and Point Platte.