The attack occurred on Wednesday May 13, between 9.50 pm and 10 pm.
A 41-year-old woman was walking along Dulwich Road, near the Brockwell Lido entrance, when was approached by two suspects.
She was then pulled into the park and raped.
The suspects, both described as white and in their 20s, left the park together through the same Lido gate.
Officers from the Met’s sexual Offences, Exploitation and Child Abuse Command are investigating and have appealed for witnesses.
Anyone with information is asked to call 020 8721 4128 or Crimestoppers anonymously on 0800 555 111.