See the Stunning Dresses Kate Bosworth, January Jones, and More Stars Wore to the Hammer Museum Gala

Hollywood's finest gathered at the Hammer Museum's 12th annual Gala in the Garden in Los Angeles on Saturday night, where more than 600 guests came together to honor Joni Mitchell and Mark Bradford. Unsurprisingly, the ensembles to hit the red carpet did not disappoint—the ladies in attendance turned out killer look after killer look, many opting for gorgeous creations by Bottega Veneta, the night's sponsor.

Kate Bosworth set the fashion bar high in a white-hot one-sleeved Alexandre Vauthier couture gown that featured a cut-out back and pearl beading (above, left), which she paired with a metallic Bottega Veneta clutch and sparkling Piaget diamonds. Meanwhile, January Jones stood out from the crowd in a hot pink Bottega Veneta frock, Stuart Weitzman sandals, and a studded clutch. "I really like to color of it," Jones tells InStyle of why she chose the look (above, center). "It’s kind of funky. I tried on a few and this one just felt more fun for the event." Never one to get it wrong, Emmy Rossum dazzled in a plunging black-and-gold Bottega Veneta design, dangling gold earrings, and a nude Bottega Veneta clutch (above, right). "It seemed fun and worthy of a museum gala," Rossum says. "It’s not usually what I wear, but I like it a lot. It makes me feel fun and glamorous."

Gorgeous in a white and metallic ensemble, Demi Moore also chose a Bottega Veneta dress and clutch for the evening along with strappy sandals. "It was easy and elegant," Moore says. Showing off her polished pregnancy style, Zoe Saldana glowed in black and purple geometric-patterned dress by Bottega Veneta that perfectly highlighted her baby bump.

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Taking an edgier approach, Jordana Brewster rocked a Bottega Veneta frock that featured paneled leather stripes. "This outfit is like a dream," Brewster shares. "I love that it’s leather and that it’s a bit different. I’m obsessed with the butterfly clutch!" Dianna Agron oozed elegance in a feminine black and nude patterned Bottega Veneta gown styled with the brand’s signature woven clutch and Neil Lane jewels. "I picked it off the rack and it was instantly my favorite. It’s completely effortless," the actress tells InStyle. "It’s one of those dresses that you want to wear to a wedding or great event because it’s not only beautiful, but you’re going to have a great time in it. You can move and dance and breathe in it."

It seemed like every star in Hollywood stepped out for the party, as the A-list crowd included Julia Roberts, Will Ferrell, Orlando Bloom, Rashida Jones, Jack Black, Elizabeth Banks, Evan Rachel Wood, Jim Carey, Ashley Olsen, Tony Goldwyn, Rita Wilson, Olivia Thirlby, Kiernan Shipka, Piper Perabo, Ireland Baldwin, and more. During the evening, guests mixed and mingled in the gallery exhibits as they enjoyed cocktails before a lavish sit-down dinner in the museum's courtyard and a performance by hit-maker Sia.

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—With reporting by Heather Newgen