The attacks occurred on July 26 and August 8 in the 6700-block of Grand Avenue and in the 7400-block of Arkansas Avenue, police said.
In both incidents, the victims were out walking when a suspect approached them, forced them into an alley and raped them.
The suspect in both cases was described as a young black male, 5'7" to 5'10" with an average build, police said. The suspect was wearing a dark hoodie and shorts in both instances and investigators believe the same person could be responsible in both crimes.
"The detectives with our special victims unit are working diligently to locate the suspect. We would like to encourage the public to be aware of their surroundings and never walk alone when possible. Also, trust your instincts. If you think you are being followed, get to a well-lit, busy area," said Hammond Police Chief John Doughty.
Anyone with information is asked to contact Hammond Police Detective Sergeant Chris Matonovich at 219-852-2963.