Katherine Noel Brosnahan was born in Kansas City, Mo., on December 24, 1962. Her father worked in construction while her mother took care of her and her five siblings. While a student at Arizona State University, where she studied journalism, she worked in a motorcycle bar and a men’s clothing store. There, she met her husband-to-be, Andy Spade, the brother of the actor and comedian David Spade. She graduated in 1985. After graduation, Ms. Spade moved to New York, where she became an assistant fashion editor at Mademoiselle magazine. Within five years she was the accessories editor. In 1993, she founded Kate Spade with Andy and a friend, Elyce Arons. She did not know what to call the company at first and decided to make it a combination of her and Andy’s names. (The couple married in 1994.) The company they founded changed hands over the years. Kate and Andy Spade sold 56% of the brand to Neiman Marcus for $33.6 million in 1999. Neiman Marcus Group sold the company to Liz Claiborne, Inc. in 2006. By 2017, when Kate Spade & Company (as the former Liz Claiborne, Inc. eventually came to be known) was acquired by Coach, Inc., Mr. and Ms. Spade had been gone for more than a decade, having left to devote themselves to other projects. Ms. Spade dedicated herself to her family and to philanthropy, through the Kate Spade & Company Foundation, which is devoted to economic equality for women. In 2016, together with her husband, Ms. Arons and Paola Venturi, a Kate Spade alum, Ms. Spade launched a new venture, an accessories label called Frances Valentine. She was so committed to the project that she added Valentine to her name. She is survived by her husband, and daughter, Frances Beatrix.