The image shows welts on the woman's forehead above each of her eyebrows, marks on her cheek and around her lips and general swelling. TMZ did not say how it obtained the photo, when it was taken or by whom.
Asked whether it could confirm the photo's origin, Los Angeles Police Department Officer Jason Lee said only that the agency hasn't released any images of the woman who accused Brown, and will not release evidence photos. A spokesman for the Los Angeles County District Attorney said all evidence related to the case against Brown is still with police.
Brown was arrested Feb 8 and booked on suspicion of making felony criminal threats to a woman that authorities have not publicly identified. A person familiar with the situation, who was not authorised to speak publicly on the matter and requested anonymity, confirmed that the woman was Rihanna, whose real name is Robyn Fenty.
The person said some of the injuries shown in the photo - specifically the marks on the woman's forehead - were consistent with the injuries Rihanna sustained.
Prosecutors have asked police to provide more information before deciding whether to press charges against Brown. Police have said the 19-year-old singer could face domestic violence charges if prosecutors think they are appropriate.
The woman in the photo posted by TMZ has a tattoo of Roman numerals on her left shoulder; Rihanna was photographed by The Associated Press the night of the incident with a tattoo of the same numerals on the same shoulder.
TMZ had previously used its site to debunk a manipulated image that depicted Rihanna with a black eye.
No public statement has been issued on behalf of Rihanna, who turns 21 on Friday. Email and telephone messages left late Thursday with representatives for both Brown and Rihanna were not immediately returned.
Brown released a statement on Sunday, which read in part, 'Words cannot begin to express how sorry and saddened I am over what transpired.' The statement, which did not mention Rihanna, said that Brown was consulting with loved ones, his mother and pastor.
Brown's arrest came roughly 18 hours after he and Rihanna left a pre-Grammy party honoring music mogul Clive Davis. According to police, Brown and a woman were involved in an altercation in a car travelling through the upscale Hancock Park neighbourhood shortly after midnight. Police have said the woman had visible injuries, and that Brown was gone from the scene when they arrived. -- AP