A new doctor is set to arrive at Grey Sloan Memorial Hospital in the season 18 premiere of 'Grey's Anatomy'.

According to Deadline, Peter Gallagher is joining the cast of 'Grey's Anatomy' in a recurring role.

TV fans will know the actor best for his role as Sandy Cohen in teen drama 'The O.C.'

He also starred on 'Law & Order: Special Victims Unit', 'New Girl', 'Zoey’s Extraordinary Playlist', and 'Grace and Frankie'.

His movie roles include 'American Beauty', 'While You Were Sleeping', and more recently, 'Palm Springs'.

Gallagher's 'Grey's Anatomy' character is called Dr. Alan Hamilton.

He knew Ellis Grey (Kate Burton) in the past and meets Meredith (Ellen Pompeo) in the next season's first episode.

It was previously announced that Ellis will be reintroduced on 'Grey's', with Kate Burton reprising the role.

It's likely that the season premiere will include flashbacks to depict Ellis and Alan's relationship.

Season 17 of 'Grey's Anatomy' included the return of a number of fan favourites, which went down a treat with viewers and is likely part of the reason why Ellis is being written back into the show.

Season 18 of the medical drama debuts on ABC on September 30th.