The couple have been inseparable since meeting on the 2007 film Evening.
Check out other couples who hooked up while working together.
At the NYC premiere of Confessions of a Shopaholic, Dancy explained to Us what he looks for in his perfect girl. He told Us, "Someone who's intelligent, somebody who makes me laugh. I know people always say a good sense of humor, but they're usually lying. Somebody who kind of has an independent life and ambition."
Would Dancy -- who appears opposite Isla Fisher in Shopaholic -- consider making another film with his bride-to-be?
"Never say never," he told Us at the Sundance Film Festival. "There's no list of people I wouldn't work with, up to and including Claire. Obviously, I respect her as an actress immensely!"
See which other celebs are engaged in '09!
No word yet on when Danes, 29, and Dancy, 33, plan to walk down the aisle.