From a steamy onscreen affair to a real-life engagement!

Mad Men costars Alexis Bledel andVincent Kartheiser are engaged to be married, a rep for the actress tells E! News.

The 31-year-old former Gilmore Girls star and her 33-year-old beau made their red carpet debut back in October, where they looked blissfully in love and incredibly happy to be together.

Alexis Bledel attends Amber Tamblyn's wedding
Bledel played an unhappy housewife in a series of episodes on the hit AMC series, where she seduces Kartheiser's seedy character Pete Campbell.
This will be the first marriage for the good-looking couple. No further details about the I-dos have been revealed.

Us Weekly first reported the engagement news, and sources tell the mag Vincent "proposed a few weeks ago" and the ring is "huge."

Congrats, you two! Can't wait until Bledel debuts the bauble!