Kate Walsh is returning to 'Grey's Anatomy'.

Kate Walsh

Kate Walsh

The 53-year-old actress is "so excited" to be returning to Grey Sloan Memorial Hospital as Dr. Addison Montgomery in the upcoming 18th season of the ABC medical drama series.

In a video shared on the show's Twitter page, Kate said: "Well, well, well, would you look who it is. That's right, my loves, Dr. Addison Montgomery is coming back to Grey Sloan Memorial Hospital and I'm so excited to be home again joining Shonda [Rhimes, creator], Ellen [Pompeo, star] and the rest of the incredible cast.

"This season — 18, whew! — Just wait until you see what she has in store for you. The new season premieres September 30 on ABC."

Kate first appeared on the show in the season 1 finale, with Addison being the estranged wife of Patrick Dempsey's character, Dr. Derek Shepherd.

She stayed on as a regular for another two seasons before her neonatal surgeon character led spin-off series 'Private Practice, which ran from 2007 to 2013, and she continued to make occasional guest appearances on 'Grey's Anatomy' during that time.

Kate admitted earlier this year she would "absolutely" return to 'Grey's Anatomy' if the writers made it possible.

She said: "If they could get it done, I'd be happy to come back. It definitely changed my life."

Kate also insisted she knew from season one that the show would be huge.

She said: "Sometimes I do feel like I get a little witchy about things.

"I was like, 'This is a great show.' Even before it even had an airtime. I was just on as a guest, I was like, 'This is a great show. I think it's going to be really good.' And here we are. Here they are."

Season 18 will also mark the return of Kate Burton, who will reprise her role as Dr. Ellis Grey, the mother of Ellen's character Meredith Grey.

Season 17 saw a host of familiar faces return to the show, including Patrick, T.R. Knight, Chyler Leigh and Sarah Drew.