His publicist Matthew Hiltzik made the engagement announcement over Twitter.
Baldwin, who once starred in a film called "The Marrying Man," turns 54 on Tuesday and an engagement, says Hiltzik, is a "great way to celebrate!"
Baldwin was previously married to Kim Basinger. They have a daughter together named Ireland. He published a book in 2008 called "A Promise to Ourselves" about his personal experience dealing with divorce and his battle with Basinger over custody of their daughter.
