The freehold of the Simon the Tanner pub in Long Lane has been purchased by the local United St Saviour's Charity.
The pub has had a chequered recent history with long periods of closure, but reopened under its present management two years ago.
"The income that we receive from these pubs helps to support Southwark pensioners through our almshouse provision and local community organisations through charitable grants."
Julie Friel, the pub's leaseholder, said: "We welcome St Saviour's as a freeholder that is committed to improving the local community.
"It means that we can focus on our aim of delivering good beer, good food and a great community pub."