The River Effra is a tributary of the River Thames in London, England. It originates in the area of Crystal Palace and flows northward through several neighborhoods, including Brixton and Herne Hill, before joining the Thames at Vauxhall. The river is approximately 9 miles long and has been largely culverted, meaning it flows underground in many sections. Historically, the River Effra was an important waterway for local communities, providing water for drinking and agriculture. Today, it is mostly hidden from view, but efforts have been made to restore parts of the river and improve its ecological health, highlighting its significance in London's natural history.