The former EastEnders actress and Cockneys Vs Zombies star plays Sally Bowles opposite Will Young's Emcee in Rufus Norris's adaptation, which opens at London's Savoy Theatre on October 3 after its regional tour.
"I started doing musical theatre when I was 10, so I'm very excited," Ryan told Stylist.
"The writing is timeless; we are are performing it years later yet it still has such impact and relevance."
She added: "I love the physicality. My dream role is where I learn a new skill
"It's always been a calling for me. This role feels like I'm moving in the right direction. I'm starting a brilliant new chapter in my career."