Star Sightings: Lorde Wows the Crowd at Life is Beautiful Festival, Ariana Grande Dances in Hong Kong & More!

Lorde at Life Is Beautiful festival
Jeff Kravitz

From partying in Vegas to visiting the great outdoors, see how A-listers are living it up as fall kicks off.

From popping bottles in Vegas to tons of birthday celebrations and fun performances, celebs are kicking off fall right!

Lorde made the crowd feel anything but blue during her performance on the first night of the Life is Beautiful Music and Art Festival in Las Vegas on Sept. 22, performing her hits like “Green Light” and “Royals.” The night was closed out by blink-182 and Chance the Rapper.

Jeff Kravitz

Following his Saturday afternoon set at Marquee Dayclub in the Cosmopolitan of Las Vegas, DJ Khaled was briefly joined by Kesha at a private dining room at TAO Asian Bistro in the Venetian on Sept. 23. The “Praying” singer, who was in town to perform at the iHeartRadio Music Festival, congratulated Khaled on his festival performance before heading to her own table in the restaurant’s loft, where she enjoyed the chicken fried rice, lobster wontons and short ribs. As for the producer, he and a group of 20 noshed on sea bass, orange chicken and spicy tuna.

Ivan Barrios

Rounding out Sin City's visitors were Bachelor and Bachelorette stars Dean Unglert, Peter Kraus, Becca Tilley, Ashley Iaconetti and Wells Adams, who hit up Planet Hollywood Resort & Casino’s 10-Year Celebration on Sept. 21, sipping on cocktails at Heart Bar before meeting up with Ben Higgins for dinner at Gordon Ramsay Burger, where they dined on burgers and treated themselves to desserts like the Crème Brûlée Shake and Brown Butter Caramel Pecan Shake.

David Becker

Ariana Grande wrapped up her Dangerous Woman tour by launching her partnership with Reebok in Hong Kong on Sept. 21. She held a dance class with her choreographers and creative directors, Brian and Scott Nicholson, and fans also got the chance to workout with her trainer, Harley Pasternak, or get a styling session from her stylist, Law Roach.

Reebok

Back in L.A., Kelsea Ballerini “unapologetically” enjoyed her day at Universal Studios Hollywood on Sept. 26.

Ron Mateo/Universal Studios Hollywood

There were major birthday celebrations going on as well. Tatiana Maslany celebrated her 32nd at The Lure Group's Seaport Food Lab alongside boyfriend Tom Cullen on Sept. 22. The Downton Abbey star even surprised his leading lady with a "WTF" red velvet waffle cake from Clinton Hall.

Pitch Perfect sweethearts Skylar Astin and Anna Camp celebrated their birthdays at Bowlmor Chelsea Piers in New York City last weekend. Astin was born on Sept. 23 and Camp's big day is just four days later, but the spotlight at the dual soiree was on Astin, as it was his milestone 30th birthday. Sources say the group of six included his family, and that the married duo was very cute all evening long, “taking selfies and looking very much in love.”

Karrueche Tran gave Christina Milian a big smooch on the cheek when the pals celebrated Milian’s birthday at Beauty and Essex in Los Angeles on Sept. 26. Both ladies were rocking rings by George the Jeweler to amp up their party outfits.

Kevin Wong

And Jason Derulo celebrated his 28th birthday a little early, stopping by 1 OAK Nightclub inside The Mirage in Las Vegas -- where Flo Rida and Flava Flav were also hanging out -- with a large group of friends around 1:30 a.m. Sources tell ET that the “Marry Me” singer, clad in an all-black ensemble, was in high spirits, dancing at his VIP table and enjoying cocktails before heading out around 3 a.m.

There was also plenty of partying to be had at hot spots in Los Angeles. Halsey and her boyfriend, G-Eazy, were front and center at Warwick in Hollywood on Sept. 20. The musical couple mingled with friends in a barricaded private booth inside the venue before performing a few of their hits around midnight.

Jamie Foxx was spotted having dinner with a large group at West Hollywood hot spot Catch LA that same night, while Mark Ballas and BC Jean of Alexander Jean brought down the house at Los Angeles’ Hotel Cafe on Sept. 20. The married performers were joined onstage by Ballas’ current Dancing With the Stars partner, Lindsey Sterling, and were supported in the audience by pals like Bethany Mota, Nikki Bella and Artem Chigvintsev.

Also taking the stage was Machine Gun Kelly, who hosted an intimate private show in collaboration with ICM at the lavish Peppermint Club in Los Angeles on Sept. 18.

Getty Images for Interscope Records

Derek Hough got away from Hollywood, basking in the outdoors with a visit to the Indiana Dunes National Lakeshore in Porter, Indiana, on Sept 26. The World of Dance judge headed to the midwest as part of the National Park Service and National Park Foundation’s Parks 101 series, which helps feature lesser-known stories from the 400 national parks.

Daniel Boczarski/Getty Images for National Park Foundation

Jenna Dewan Tatum headed outside as well, sipping on KeVita's new blueberry basil kombucha during a picnic on Sept. 21.

Olympic gold medalist Shawn Johnson East hosted an Everyday Heroes Workout event with Livestrong.com and Del Monte for 50 health, wellness and fitness enthusiasts at Calamigos Ranch in Malibu, California, on Sept. 21. The guests received first-hand tips from the gymnast on how to train like an Olympian!

Joe Perri/Livestrong.com

Also enjoying the sun was Michelle Monaghan, who kept her eyes protected with MOSCOT's MILTZEN shades as she spoke onstage during the 2017 Global Citizen Festival.

Theo Wargo/Getty Images for Global Citizen

Kim Kardashian West was spotted leaving the Nexxus salon in New York City after picking up protein treatments for her newly bleached hair. Insiders told ET that the mom of two loves to experiment with hair colors during fashion weeks. “Whether it’s Paris or New York, it’s her favorite time to try something different,” they said.

Michael Simon

Talk about a silver streak! Naomie Harris stepped out in a crushed-lamé blouse and matching pleated trousers from the Fall 2017 Michael Kors Collection to celebrate the Michael Kors Sexy Ruby launch party in London, England, on Sept. 21.

Dave Benett/Getty Images for Michael Kors

Also on the fashion front, Tyra Banks took the mainstage at the National Retail Federation’s three-day Shop.org “This is Digital” conference at the L.A. Convention Center on Sept. 26, speaking about her strengths as a businesswoman and how her life has evolved since she first started her modeling career.

Jessica Yurinko/National Retail Federation

Kelly Osbourne and Mel B were among the celebs who stepped out for a good cause, supporting the 8th Annual Face Forward Gala, presented by Etihad Airways. Osbourne was presented with the Voice Award by her friend, ET’s Keltie Knight, while the America’s Got Talent judge, who brought her mom with her to the soiree, was surprised with an award from co-founders that recognized her efforts to end violence. The Face Forward organization provides pro-bono reconstructive surgeries to survivors of domestic violence, human trafficking and other acts of crime.

Rony Armas

Accompanied by his sister, Willow, JUST water co-founder Jaden Smith held on tight to his drink at the 27th Annual Environmental Media Association awards in Los Angeles on Sept. 23.

Getty Images

Brooklyn 99’s Stephanie Beatriz tried on a Mission Belt on for size at GBK's Emmy's gifting suite. For every celeb that donned the accessory during the event, Mission Belt donated a belt to those affected by Hurricane Harvey.

Jeffrey Bertollini

After doing so much good, sometimes you need just kick back and imbibe. Mila Kunis, a global brand partner for Jim Beam Whiskey, looked stunning at the official launch party for Jim Beam Vanilla in New York City on Sept. 25.

Michael Loccisano/Getty Images for Jim Beam

A$AP Rocky celebrated a successful kickoff to the A$AP Mob Tour at the official after-party hosted by Courvoisier cognac, for which the rapper is a brand ambassador, in New York City on Sept. 25.

Audiotree.tv

Also newly anointed brand ambassadors, Migos popped some Luc Belaire Gold bubbly before their show in early September.

Garrett Bruce

The cast and executive producers of Grey’s Anatomy had reason to celebrate as well. They were joined by ABC Executives Channing Dungey and Patrick Moran for a cake-cutting ceremony at the taping of the hit drama’s 300th episode on the show's Los Angeles set on Sept. 26.

Eddy Chen/ABC

Not only that, but Steven Spielberg and Christopher Nolan celebrated the 75th anniversary of the Golden Globe Awards with the Hollywood Foreign Press Association, Film Foundation and American Cinematheque at The Egyptian Theatre in Los Angeles last week.

Hollywood Foreign Press Association

Meanwhile, Kellogg’s teamed up with celeb chef Jessica Koslow for a special limited-run event at her popular Los Angeles restaurant SQIRL: its first-ever brinner menu, which reimagined staples like flaky biscuits and Koslow’s famous ricotta toast with popular Kellogg’s cereals. The three-night affair was a fundraiser for Direct Relief, and they raised $5,600 for the charity.

Matt Harbicht/AP Images for Kellogg's

On the opposite coast, En Vogue’s Terry Ellis, Cindy Herron and Rhona Bennett hit the red carpet at the Finding Ashley Stewart event at Kings Theatre in Brooklyn, New York, on Sept. 16, where they told ET, “We have an album coming out [soon] called Electric Cafe, so we’re very much looking forward to that!”

Lars Niki/Getty Images for Ashley Stewart

Plus, Nas stepped out at the launch of Foot Locker and Timberland's Fall 2017 Legends Collection in New York City on Sept. 19.

Soul Brother

Click through the gallery below for even more must-see star sightings.