She leaves behind her husband, Andy, and a 13-year-old daughter, Frances Beatrix Spade.
Andy Spade was a cocreator of Kate Spade's namesake brand and played an integral role in building the business.
Famed handbag designer Kate Spade was found dead in an apparent suicide on Tuesday morning in her Upper East Side apartment, the Associated Press reported citing law-enforcement officials. She was 55.
Spade, who was best known for launching her namesake handbag brand, leaves behind a husband and a 13-year old daughter, Frances Beatrix Spade.
Andy Spade, her husband of 24 years and the brother of actor David Spade, has not yet publicly commented on his wife's death.
The couple met at Arizona State University and married in 1994. Kate Spade was the accessories editor at Mademoiselle magazine, formerly owned by Condé Nast, before she left to set up a handbag company in 1993. She did so with the encouragement of Andy, her then boyfriend.
Related: See the designer over the years:
Kate Spade through the years
Kate Spade through the years
Kate Spade during The 2001 VH1/Vogue Fashion Awards - Arrivals at The Hammerstein Ballroom in New York City, New York, United States. (Photo by Jim Spellman/WireImage)
Kate Spade during The Fresh Air Fund Salutes American Heroes at Tavern on the Green in New York City, New York, United States. (Photo by Jim Spellman/WireImage)
Designer Kate Spade arriving at the 2002 Ace Awards presented by The Accessories Council at Cipriani 42nd Street in New York City. November 5, 2002. Photo by Evan Agostini/ImageDirect.
Kate Spade during The Concert for New York City - After Party at Hudson Hotel in New York City, New York, United States. (Photo by Ron Galella/WireImage)
Kate Spade during 13th Annual Glamour Magazine's Women of the Year Awards - Arrivals at Metropolitan Museum of Art in New York City, New York, United States. (Photo by Dimitrios Kambouris/WireImage)
Kate Spade with husband and brother-in-law David Spade at the 20th Annual American Fashion Awards at Avery Fisher Hall, Lincoln Center in New York City. 06/14/2001. Photo: Evan Agostini/ImageDirect
Kate Spade during 17th Annual CFDA Awards at JP Morgan Atrium in New York City, New York, United States. (Photo by Ron Galella/WireImage)
Designer Kate Spade is photographed at her offices. (Photo by David Howells/Corbis via Getty Images)
Kate Spade and Andy Spade during Costume Institute Benefit Dance: 'Party of the Year' - Arrivals at Metropolitan Museum of Art in New York City, New York, United States. (Photo by Dimitrios Kambouris/WireImage)
Kate Spade during 14th Annual GLAMOUR Women of the Year Awards - Red Carpet at American Museum of Natural History in New York City, New York, United States. (Photo by Dimitrios Kambouris/WireImage)
Kate Spade (Photo by Carley Margolis/FilmMagic)
Kate Spade during CFDA 7th on Sale Kick-Off - Red Carpet and Inside at Sky Light Studios in New York City, New York, United States. (Photo by Rabbani and Solimene Photography/WireImage for LaForce and Stevens)
NEW YORK - JUNE 7: Designer Kate Spade attends the '2004 CFDA Fashion Awards' at the New York Public Library June 7, 2004 in New York City. (Photo by Evan Agostini/Getty Images)
Kate Spade, Andy Spade and Ruth Lande Shuman, founder/president of Publicolor (Photo by Carley Margolis/FilmMagic)
David Spade and Kate Spade during Photographer's Gallery Presents Slim Aarons Curated by Kate Spade at Fred Segal Cafe in West Hollywood, California, United States. (Photo by Chris Weeks/WireImage)
NEW YORK CITY, NY - APRIL 30: Kate Spade and Andy Spade attend PARSONS The NEW SCHOOL FOR DESIGN 59TH ANNUAL BENEFIT and FASHION SHOW Honoring SUSAN D. KRONICK, Vice Chairman, Federated Department Stores, Inc. at Grand Hyatt on April 30, 2007 in New York City. (Photo by JIMI CELESTE/Patrick McMullan via Getty Images)
NEW YORK, NY - NOVEMBER 10: Kate Spade attends the 2015 Basser Center For BRCA Benefit at Cipriani Wall Street on November 10, 2015 in New York City. (Photo by Daniel Zuchnik/WireImage)
NEW YORK, NY - APRIL 28: Kate Spade speaks on stage at Build Series Presents Kate Spade and Andy Spade Discussing Their Latest Project Frances Valentine at Build Studio on April 28, 2017 in New York City. (Photo by Monica Schipper/WireImage)
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"The reason I started making handbags was because of Andy's suggestion. After moving through a number of positions, I had been promoted to senior fashion editor after six years at Mademoiselle magazine. I wasn't sure the next step was one I wanted to make. Andy just said, 'You know, I think we should start something,'" Kate Spade told CNN Money in 2003.
The business was named after the couple's combined names, which later became her married name.
Andy, who had worked in advertising, played a supportive role in the business early on, but he quit his job in 1996 to join Kate Spade full time.
The couple built up the brand over the next few years before selling a 56% stake to Neiman Marcus for $33.6 million in 1999. In 2006 they sold Neiman Marcus the remaining stake for $59 million.
One week later, Neiman Marcus went on to sell the business for $124 million to retailer Liz Claiborne. Coach acquired the company last year for $2.4 billion.
The couple didn't give up on handbags altogether, though. In 2015 they launched a new brand, Frances Valentine, that sells shoes and handbags. The company was named after their daughter.
Related: Celebs mourn the designer's passing:
Celebrities react to Kate Spade's death
Celebrities react to Kate Spade's death
My grandmother gave me my first Kate Spade bag when I was in college. I still have it. Holding Kate’s family, frien… https://t.co/GZaUzTVkCF
The CFDA is devastated to hear the news of our friend, colleague, and CFDA member Kate Spade’s tragic passing. – D… https://t.co/kReGp7rIAS
Kate. 😢 You never know what someone is going through. Please call 24/7 Suicide Hotline 1-800-273-8255 ❤️ #katespade
Depression does not discriminate and comes without warning. RIP Kate Spade. Love to her family. National Suicide… https://t.co/IwEmNxaPbk
@DavidSpade - all my love to u dave -
The nicest woman, the first person to compliment me on Liz Lange Maternity when I first started. And the creator of… https://t.co/hmUG1yDVol
Kate Spade & her brand have always been so kind to me the past couple years & I’m crushed to hear about her passing… https://t.co/NYxrYavxt1
Kate Spade’s tragic passing is a painful reminder that we never truly know another’s pain or the burden they carry.… https://t.co/thqy9nbXeU
Very saddened to hear about the passing of Kate Spade. Mental illness does not discriminate and can happen to anyon… https://t.co/1LnxI9hmdy
I loved @katespadeny’s beautiful and whimsical fashions. So sad. Prayers to her family.
Kate Spade was more than a designer. She had a quirky visual language that captivated Bat Mitzvah girls and artists… https://t.co/1ohSdnJU3W