Katie Holmes Wears Sexy Backless Dress, Shows Side Boob at First Met Gala in Four Years

Katie Holmes attends the Costume Institute Gala for the "PUNK: Chaos to Couture" exhibition at the Metropolitan Museum of Art on May 6, 2013 in New York City. Credit: Kevin Mazur/WireImage.com

Baby got back! Katie Holmes turned heads at the Costume Institute Gala in NYC on Monday, May 6, sizzling in a completely backless Francisco Costa for Calvin Klein white gown. The usually-conservative star even flashed a bit of sideboob as she posed from the front, risking a nip slip. See more photos of Katie Holmes at the Met Gala. 

While the theme of the night was PUNK: Chaos to Couture, the actress and designer certainly steered away from the punk aspect and instead opted for a classy ensemble at the star-studded event -- pairing the flowing halter dress with diamond earrings and white stilettos. Wearing barely any lipstick, Tom Cruise's ex-wife debuted smokey eye-makeup to complement her overall sexy look.

Holmes, 34, completed the backless style with a high updo, gathering her brunette hair into a quiff. She looked poised and confident as she showed off her shoulders, smiling at photographers while entering the Metropolitan Museum of Art after getting ready at The Mark Hotel.

The former Dawson's Creek star last attended the Met Ball in 2009, with then-husband Cruise. The pair finalized their divorce last summer. With daughter Suri attending Avenues School in NYC, Holmes has been busy working on her new movie, Mania Days.

Click here to view the live stream (+ archived version) of the 2013 Met Gala on Vogue.com.