12:09PM BST 13 Jul 2011
The left-back has signed a three-year deal at Craven Cottage and will link up with his brother Bjorn Helge in west London.
Riise has spent the past three seasons in Serie A with Roma, having departed Liverpool in 2008.
The 30-year-old made more than 230 appearances for the Merseysiders after joining them from Monaco in 2001 and admits it is great to be back in England.
"I'm delighted to have completed my transfer to Fulham this morning and am looking forward to playing in the Premier League once again," he told Fulham's official website.
"Fulham is a club that I have been following as my brother, Bjorn, plays here and he speaks very highly of the club and the staff.