South Walney is one of two nature reserves on Walney Island, England. It has been managed by the Cumbria Wildlife Trust since 1963.
The reserve is notable for lesser black backed gulls and herring gulls and the only grey seal colony in Cumbria.
The reserve is the home of the Walney Bird Observatory which collates bird records from across the island. Around 300 species of bird have been recorded on Walney Island since the foundation of the bird observatory in 1964.