Hayden Christensen and Rachel Bilson
Dimitrios Kambouris/WireImage
According to a friend of the actress, the two, who costarred in 2008's Jumper, got engaged in December.
"They're so excited," says the pal, adding that no wedding date has been set. "They're a great couple. Rachel seems thrilled beyond belief."
When contacted, Bilson's rep told PEOPLE, "I don't comment on my clients' personal lives."
A rep for Christensen had no comment.
The engagement news was first reported by the New York Post's Page Six.
• Reporting by ALEXIS CHIU and LISA INGRASSIA
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