Stirling Gallacher, best known for her roles as Paula Martin in Coronation Street and Georgina Woodson in Doctors, is joining BBC's Casualty as police officer Ffion Morgan, the wife of paramedic Jan Jenning.
Fans of the medical drama have been promised "turbulent" times ahead.
As the BBC announced her casting, Gallacher said she was "entirely delighted to be joining the longest-running emergency medical drama television series in the world".
She has already begun filming and will be seen in episodes this Spring. Gallacher previously appeared as a number of characters over the years in Casualty and spin-off show Holby City.
Teasing what lies ahead for Gallacher as Ffion Morgan, Simon Harper, Executive Producer of Casualty and Holby City, said: "The audience may recall a single, somewhat loaded reference last year from Jan's son Ross to her wife Ffion and the kids back home.
"So we've had her off-screen marriage up our sleeve for some time now and are really excited to explore it - not least with an actor as distinguished as Stirling, whom we are thrilled to welcome to the Casualty company, playing alongside the brilliant Di Botcher [who plays Jan Jenning].
"Jan has a huge and terrifying story coming up in the next series where Ross comes into her life again - and given that Ross is pretty dodgy and Ffion is a police officer, it's all going to get pretty turbulent!"
Casualty airs on BBC One on Saturday nights.