Police have cordoned off an area of woodland off Aldermoor Road, opposite Aldermoor Avenue, after a woman reported she was assaulted there shortly before 8.30am this morning.
The victim was jogging through the wooded area when she was assaulted by a man who then ran off.
The man is described as in his late 20s around 5ft 10 inches tall and slim. He was wearing a black rain coat.
Anyone with information is asked to contact the Western Area CID team at Southampton Central police station on 101 or call Crimestoppers anonymously on 0800 555 111.