Police are appealing for public assistance after a woman was sexually assaulted in Sunshine last month.

Police have been told a woman boarded a route 903 bus from the Sunshine Railway Station just after 6pm on Thursday, December 27, and when she disembarked at Munroe Avenue she was sexually assaulted by an unknown man.

The man is perceived to be Pacific Islander in appearance, solid build, aged 20 to 30 years and 180cm tall with brown eyes, a black beard and long black hair in a bun.

He was wearing a white top, khaki-coloured shorts, and was carrying an Adidas backpack with a yellow logo.

Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au