Rachel McAdams, Michael Sheen Make Red Carpet Debut Together

By Cara Shultz

UPDATED 05/11/2011 at 05:30 PM EDT • Originally published 05/11/2011 at 05:00 PM EDT

They've remained coy about their romance – in spite of being spotted mid-smooch – but Rachel McAdams and Michael Sheen made their red carpet debut as a couple Wednesday at the Cannes International Film Festival.

"She's a genuinely lovely lady as well as being stunningly beautiful and very talented," Sheen, 42, told Entertainment Tonight Canada of McAdams, his costar in the Woody Allen-directed comedy Midnight in Paris, which is showing at the festival.

The actress, 34 – who was recently spotted wearing a ring on her wedding finger – isn't engaged to Sheen, but she recently talked to Elle about her hopes for a "fairy-tale romance."

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"[My parents are] still together and still in love," she said. "I'm very blessed that way. I had a great example of love in front of me, and that's probably what makes me such a romantic."

McAdams chose a Marchesa dress for the debut, which had a five-foot train that trailed the steps as she climbed to the theater. At ease and in sync with his date, Sheen bent down to straighten it out for her when she stopped to wave to the crowds.

• With Reporting by PETER MIKELBANK