The River Effra is a subterranean river located in south London, England.

When the London sewerage system was constructed during the mid-19th century, its designer, Sir Joseph Bazalgette incorporated flows from the River Effra into his 'high level interceptory sewer', also known as the Effra sewer, running from Herne Hill eastwards under Peckham and New Cross to Deptford.

The main course of the River Effra was diverted into a sewer and culverts. It can be accessed through the sewers on Effra Road in Brixton, South London.

The river rises near Crystal Palace, London, then flows through Norwood and then Brixton before emptying into the River Thames near Vauxhall Bridge.

See also

• Subterranean rivers of London
• Rivers of the United Kingdom