A 13-year-old girl was grabbed and attacked her as she walked through a park, say police.
The teenager managed to fight off the man, who grabbed her from behind while out walking in Westleigh Park earlier today.
Now police have launched an appeal to trace the man, who struck just before 9am.
The young victim managed to struggle free and run home, where police were alerted.
Police say the man was tall, white, of medium build and around 30 years-old, with short dark hair and a scruffy beard. He is also described as having muscular arms and a big nose.
He spoke with a foreign accent, possibly Eastern European and was wearing a green jacket, a top with "King" written on it and black Adidas tracksuit bottoms with stripes down the side.
Det Chief Insp Clare Devlin from Wigan CID, said: "Thankfully this brave young girl was able to fight off the man and run away to safety. She has obviously been left frightened by this experience and my thoughts are with her and her family.
"We have launched an investigation and are very keen to speak to anyone who may have witnessed the incident or may have seen a man matching this description acting suspiciously in the area.
"Incidents like this are thankfully incredibly rare, the local community are bound to be very concerned however, so I would like to reassure them that we are doing all that we can to identify this man.
"We have increased patrols in the area and anyone with any questions or concerns is encouraged to come and speak to our officers."
Anyone with any information is asked to contact police on 0161 856 7103, alternatively call 101 or the independent charity Crimestoppers anonymously on 0800 555 111.