The assault and robbery were reported around 9:20 p.m. Tuesday in the 300 block of Turk Street.
Police spokesman Officer Albie Esparza said the 30-year-old victim and his girlfriend had an argument on the street, but quickly made up and began hugging and kissing while lying on the sidewalk.
At that point, a man and woman approached and, for no apparent reason, began punching and kicking the victim, Esparza said.
The male suspect then reached into the victim's pocket and grabbed his wallet, then the pair fled west toward Hyde Street, he said.
The victim was taken to a hospital to be treated for his injuries, which included a laceration over his right eye and bumps to his head.
The victim and his girlfriend said they did not know the pair responsible for the attack and robbery, according to Esparza.
The male suspect was described as a black man around 40 years old who is about 5 feet 8 inches tall and weighs 300 pounds, with brown hair and brown eyes. He was wearing a gray hooded sweatshirt and blue jeans.
The female suspect was described as a black woman, also around 40 years old, who is about 5 feet 5 inches tall, weighs around 200 pounds with brown hair and brown eyes and was wearing all-black clothing, Esparza said.
Anyone with information about the case is encouraged to call the Police Department's anonymous tip line at (415) 575-4444 or send a tip by text message to TIP411.