Greta Gerwig has sealed the deal with her very own Ken ... marrying Noah Baumbach after 12 years of dating!
After exchanging vows at NYC's City Hall Tuesday, the directors celebrated at Billy Joel's Madison Square Garden concert -- Greta was still wearing her bridal white, and Noah his dashing navy blue suit, as they cheered at the concert.
Greta was heard sharing the happy news with folks backstage, according to Page Six ... with a source telling them the newlyweds were glowing and so happy.
Marriage was a long time coming for the pair ... who began dating in 2011, and got engaged in 2020.
They're also parents to son Harold, 4, and another baby boy, who they welcomed earlier this year.
This rounds off a massive year for Greta -- the first female director to have a film cross the billion-dollar line with the phenomenal success of "Barbie."