Hollywood A-Listers Hop Across the Pond for London's Biggest Soiree of the Summer

were a stylish trio at the Serpentine Gallery Summer Party in London, England. The ladies all dressed to the occasion: Chung in Erdem, Knightley in Chanel, and Delevingne in Mulberry.

treated guests to a surprise performance at the Serpentine Gallery Summer Party, where he sang his hits and showed off his dance moves in a Brioni suit on stage.

got cozy at the Serpentine Gallery Summer Party held in the heart of the Royal Park of London's Kensington Gardens. Waterhouse glowed in a pale pink Burberry Prorsum gown, while Cooper kept it simple in a suit.

also struck a pose at the Serpentine Gallery Summer Party, where she dazzled in a red Givenchy number.

joined the Serpentine Gallery Summer Party in a look by Brioni, the event's sponsor. The annual celebration unveiled a pavilion designed by Chilean architect Smiljan Radic: a fragile white fiberglass cocoon resting on top of a ring of boulders.

looked regal at the Serpentine Gallery Summer Party, one of the highlights of the London's social calendar. Beatrice wore a flower-adorned Nicholas Oakwell Couture dress, while Eugenie donned a Burberry frock.

were fashionably bright at the Mr. Clean Summer Fashion Party in New York City. Brewster looked lovely in a warm weather-ready crop top and skirt by Houghton, and Goreski was stylish in an orange jacket.

celebrated the launch of Virgin Atlantic’s new Vivienne Westwood uniform collection at Village Underground in London, England. For the bash, she wore a floral frock by Westwood.

attended the premiere of A Long Way Down in New York City. The duo stars in the film, which comes to select theaters July 11, 2014.

made a great trio at the Los Angeles premiere of Tammy, in which they all star. The comedy hits theaters July 2, 2014.

supported a good cause at the 2014 Ignite Gala benefiting BAM Education in New York City. For the charity event, Liu stunned in an embellished gray frock by Andrew Gn.

celebrated the launch of Michelle's debut book Letters, To The Men I Have Loved at an intimate dinner sponsored by Samsung Galaxy in Los Angeles.

came out for the premiere of Lionsgate Films' America in Los Angeles. The movie comes to theaters July 2, 2014.

celebrated at the 2014 BET Awards in Los Angeles. Williams was on-hand to perform at the ceremony and accept the trophies for Best Male R&B/Pop Artist and Video of the Year, while Washington (in Dolce & Gabbana), presented one of the night's awards.

attended Debra Lee's 2014 BET Awards pre-party at Milk Studios in Los Angeles, California. The young star stunned in a Peter Pilotto dress and bold red lip.

stepped out in a black-and-white Honor dress for the Mad Men Cast and Crew Wrap Party presented by Johnnie Walker and Brooks Brothers at The Roosevelt Hotel in Los Angeles.