The pretty actress, 27, shared her good news with her 529,000 Instagram followers when she posted a single shot of her big day.
The message simply stated the date of the wedding: "9.19.15."
In the picture, Allison looks STUNNING in a traditional white wedding gown and veil, alongside her businessman beau, 34, who was dapper in a black suit and tie.
Understandably, the groom is staring lovingly at his new wife. Lucky man!
Allison - who is famous for playing uptight Marnie Michaels - wore a beautiful Oscar de la Renta gown at the rural event, thought to be held in Wyoming.
Allison's Girls castmates Lena Dunham, Zosia Mamet and Jemima Kirke were there to see their friend get hitched.
Katy Perry was also reportedly in attendance, while Tom Hanks was even said to have officiated at the wedding!
His wife Rita Wilson plays Allison's on-screen mother in the popular HBO series.
Allison began dating Ricky Van Veen, the co-founder of CollegeHumor, in 2011. They got engaged last year.
A huge congratulations to the happy couple!
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