Police say the victim was a 21-year-old woman from upstate Edwardsville, Pennsylvania.
According to investigators, she left a home on York Street and was followed into the park.
"She became aware of a male that was behind her. The male called out to her as if he knew her," said Capt. John Darby of the Philadelphia Police.
She didn't recognize him and continued into the park for her morning jog.
Near Edgely and Reservoir he showed up again, police say, dragged her into a secluded area, and raped her.
The suspect is described as a black man with a mustache, around 50 years old, 5'8" tall, and was wearing a blue t-shirt and blue jean shorts.
Police are asking anyone who may have seen a man matching that description following a woman on the 3200 block of York Street around 7:30 a.m. on Sunday. If you saw anything, you are urged to contact police right away.
This is the second rape reported this month in the sprawling park system.
On the evening August 11, a 34-year-old woman said she was raped while preparing to jog near Bells Mill Road and Forbidden Drive. She could not give police a detailed description, except to say her attacker wore white gardening gloves, dirty blue jeans, and construction boots.
Police stopped short of saying either of the two rapes this month are connected, or saying they are connected to the co-called "Fairmount Park Rapist," who struck between 2003 and 2007.
Authorities have widely circulating sketches of that man. DNA evidence linked him to four attacks.
In July of 2007, the body of 30-year-old medical student Rebecca Park was discovered in shallow grave. She had been raped and strangled.
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