Garda detectives want to speak with a man seen in the Sandycove area on Dublin's southside on the night a woman was seriously assaulted late last month.
It happened on the seafront in the early hours of Monday, May 25.
Gardaí are releasing only limited information about the attack three weeks ago as they make this witness appeal.
The woman was attacked shortly after midnight, early on Monday, May 25, near the seafront in Sandycove.
Detectives at Dún Laoghaire want to speak to one man reported to have been seen on his own in the area that night.
He is described as white with dark hair, five foot seven in height, and of average build. He was wearing a hooded top.
Gardaí say people who were in the Sandycove area between midnight and 1.30am that morning may have seen something.
They are making a special appeal to taxi drivers, food delivery workers and joggers who might have been out.