Kelly Grier, 48, was appointed to be chairman and managing partner of Ernst & Young LLP, an appointment which distinguishes her as the  firm’s first woman to lead the company in the United States.

Until her promotion Ms. Grier served as the central US regional managing partner for EY. She will replace Steve Howe, the current chairman, on July 1, 2018. When Grier takes over it will make her the third female head at the Big Four accounting firms. Deloitte and KPMG have both had women at the helm since 2015, Cathy Engelbert and Lynne Doughtie, respectively. Only PwC is led by a man, Tim Ryan.

“Kelly was the best choice to lead us forward,” Mr. Howe said in an interview. “We’re very proud of our focus on diversity and inclusion.”

Ms. Grier has been at EY since 1990, and was promoted to US regional managing partner in 2015. She was the company’s vice chair of talent for the Americas and was also a managing partner at EY’s office in Chicago. She has also worked in Switzerland and Germany.

EY, and other major accounting firms, are international umbrella organizations. They have separate member companies in each different country where they have operations. Ms. Grier will lead the US firm, plus serve as the managing partner of EY’s Americas region. EY’s global chairman and CEO is and will remain Mark Weinberger.

“Kelly has demonstrated uncompromised integrity and an ability to manage high-performing teams, while delivering exceptional results for EY clients,” Mr. Weinberger stated.