Celebrity Celebrity Parties: October 25 to October 31, 2013 By InStyle Editors InStyle Editors Facebook Instagram Twitter Our editors and writers comprise decades of expertise across the beauty, fashion, lifestyle and wellness spaces in print and digital. We prioritize journalistic integrity, factual accuracy, and also having fun with every story we share. InStyle's editorial guidelines Updated on November 1, 2013 @ 12:36PM Pin Share Tweet Email Trending Videos Photo: Michael Buckner/Getty Celebrity Parties: October 25 to October 31, 2013 01 of 18 Ewan McGregor Yui Mok/PA Wire/ABACAPRESS.COM stepped out to attend the first UNICEF UK Halloween Ball at One Mayfair in central London. Among the 400 guests, McGregor was also joined by Claudia Schiffer and Cat Deeley as they helped raise funds for Syrian children and supply them with water, essential vaccines, education and psychological support. 02 of 18 Mark Badgley, Sigourney Weaver and James Mischka Andrew Toth/FilmMagic attended the American Ballet Theatre 2013 Opening Night Fall Gala at the David H. Koch Theatre in Lincoln Center in New York City. "They bring the most beautiful dance all over the world and I'm very proud that they're the American Ballet Theatre," Weaver (in Badgley Mischka) told InStyle.com during the gala."I never got to do anything fun like this, so I'm going to see every ballet and every opera I can." 03 of 18 Princess Charlene of Monaco Harel Rintzler/PatrickMcMullan.com/Sipa USA paid tribute to Princess Grace of Monaco at the Princess Grace Awards Gala held at Cipriani 42nd Street in New York City. Princess Charlene (in Ralph Lauren) celebrated the annual gala which granted awards to the winners of this year's Princess Grace Awards. The organization has granted over 800 awards to emerging artists in theater, dance and film. 04 of 18 Naveen Andrews, Naomi Watts and Oliver Hirschbiegel Evan Agostini/Invision/AP celebrated the premiere of their upcoming film, 'Diana' hosted by The Cinema Society at the SVA Theater in New York City. Watts (in Michael Kors and Harry Winston earrings and bracelet) and Andrews stars in the biographical film about the late Princess of Wales directed by Hirschbiegel. Following the screening, the after party took place at The Skylark where guests enjoyed Vikingfjord cocktails aptly named The Windsor, Royal Violet and Her Majesty. The film opens everywhere on November 1st. 05 of 18 Jessica Alba and Cash Warren Donato Sardella/WireImage made a date night out of the Kenzo Kalifornia launch dinner and party at The Berrics in Los Angeles. Alba (in Kenzo) and Warren were also joined by Rashida Jones and new mom, Fergie. 06 of 18 Jason Sudeikis and Olivia Wilde Michael Buckner/Getty wore masks for the first annual UNICEF's Masquerade Ball held at Hollywood Forever in California. The expecting couple were also joined by Zooey Deschanel and Ahna O'Reilly and helped raise more than $192,000 for UNICEF's programs and initiatives around the globe. 07 of 18 Selita Ebanks Robert Pitts/Landov went glam for Gabrielle's Angel Foundation's Angel Ball 2013 at Cipriani Wall Street in New York City. "Green is my favorite color," Ebanks told InStyle.com about her Roberto Cavalli dress. "It's so perfect for the holiday season, so I'm kicking it off." The ball helped raise funds and honored those who made contributions to leukemia, lymphoma, and other related cancer research for Gabrielle's Angel Foundation for Cancer Research. 08 of 18 Nikki Reed, Molly Sims and Rachel Bilson Donato Sardella/Getty attended the Chloé Los Angeles Fashion Show & Dinner hosted by Clare Waight Keller at The Brody House in Beverly Hills, California. Reed, Sims and Bilson (all in Chloé) were also joined by January Jones, Zoe Saldana and Alessandra Ambrosio. 09 of 18 Celine Dion and Alexander Wang Larry Busacca/Getty posed together at the Pandora Presents Celine Dion concert at The Edison Ballroom in New York City. Dion gave a private concert to celebrate her upcoming album 'Loved Me Back to Life,' which drops on November 5th. 10 of 18 Alfre Woodard Stephen Lovekin/Getty celebrated 20 years of legal victories defending the human rights for women worldwide at the Center for Reproductive Rights 2013 Gala at Lincoln Center in New York City. The event also raised nearly $1 million for the organization and featured notable guests including Woodard, Joan Jett, Nanette Lepore and Katie Lee. 11 of 18 Michael Polish and Kate Bosworth came out together for the premiere of their new film, 'Big Sur' presented by Brooks Brothers and SK-II at Landmark Cinemas in New York City. The film is an adaptation of Jack Kerouac's 1962 novel of the same name directed by Polish. "I think (Kerouac) would be very proud of this film," Bosworth (in Christopher Kane), who stars as Kerouac's love interest Billie, told InStyle.com. "I can say that with confidence because I think there's something that (Polish and Kerouac) know of each other -- that lonesome kind of feeling." After the premiere, the cast celebrated at the Hotel Chantelle Rooftop where Purity Vodka cocktails were served. The film opens everywhere on November 1st. 12 of 18 Justin Long and Amanda Seyfried Dimitrios Kambouris/Getty made a date night out of the 2013 Labyrinth Theater Company Celebrity Charades Benefit Gala in New York City. Long and Seyfried were also joined by couple Rose Byrne and Bobby Cannavale and spent the night playing charades to raise money for the theater company. 13 of 18 Ciara Bob Levey/Getty Images for Moet & Chandon celebrated her 28th birthday party with Moët & Chandon at Hotel Derek in Houston, Texas. The R&B singer (in Alon Livine) also showed off her 15-carat engagement ring from fiance, rapper and producer Future, who also helped design the ring with Avianne & Co. jewelers. 14 of 18 Asa Butterfield and Hailee Steinfeld Eric Charbonneau/Invision for Summit Entertainment/AP celebrated the premiere of their upcoming film, 'Ender's Game' in Los Angeles. Butterfield and Steinfeld (in Saint Laurent) both star in the movie adaptation of the 1985 novel, which follows Ender (Butterfield), an unusual gifted child who is sent to an advanced military school to prepare to save the world from an alien invasion. The film opens everywhere on November 1st. 15 of 18 Allison Williams and Zosia Mamet Walter McBride/Getty attended the benefit reading of Beth Henley's Pulitzer Prize winning play, 'Crimes of the Heart' at the Acorn Theatre in New York City. The 'Girls' stars both read from the play, which is a tragic comedy about the three MaGrath sisters, Meg, Babe and Lenny who reunite in Mississippi after Babe shoots her abusive husband. 16 of 18 Diane von Furstenberg Astrid Stawiarz/Getty stepped out for the 2013 WWD Apparel and Retail CEO Summit Dinner at The Pierre hotel in New York City. The fashion designer was joined by Rachel Roy and Anna Sui. 17 of 18 Mariah Carey and Patti LaBelle Bennett Raglin/BET/Getty came together for BET's annual Black Girls Rock! event held at the New Jersey Performing Arts Center in Newark, New Jersey. Carey (in Alexander McQueen) presented LaBelle the Living Legend Award and was also joined by Jennifer Hudson, Queen Latifah, Kelly Rowland and Michelle Williams. 18 of 18 Alain Bernard, Krysten Ritter and Nicolas Bos Michael Buckner/Getty came together for 'A Quest for Beauty: The Art of Van Cleef & Arpels' exhibition at the Bowers Museum in Santa Ana, California. Ritter (in Katie Ermilio) was joined by Bernard (President and CEO of the Americas) and Bos (Global CEO & Creative Director) for a private curated tour of the exhibit which features over 200 items from the brand's private collection along with pieces worn by Princess Grace Kelly and Elizabeth Taylor. The exhibit is now open until February 15th.