Hopton's Almshouses - founded 260 years ago by fishmonger Charles Hopton for "poor decayed men of the parish", has removed its ban on women applying to live in the Hopton Street homes.
Under the old rules, only men or couples (one of whom had to be a man) could apply to live in the picturesque homes just off Southwark Street.
"The no-women rule was out-of-date, discriminatory and, in our specific case, illegal," said Philip Sturrock, chair of the United St Saviour's Charity which took over the trusteeship of the almshouses last year.
"We are abolishing it with immediate effect."
"We would like to thank our colleagues in the Charity Commission for permitting this change, showing that tradition and innovation can walk hand in hand."
Leslie Gay, who lives at Hopton's, said: "As residents we were formally consulted on the proposed change.
"The vote was 17 residents in favour of ending the men-only rule, and only one against.
"We are proud to be creating an almshouse for the 21st century."
The United St Saviour's Charity manages two almshouses: Hopton's in Hopton Street and St Saviour's Court in Purley. Prospective residents must have lived in Southwark for the last three years and be aged 60 or over.
Applicants should contact Elizabeth Caccamo, St Saviour's Court, 2a Old Lodge Lane, Purley, CR8 4ER; email: firstname.lastname@example.org or call 020 8645 6720.