Marcia Sells — a former dancer who became an assistant district attorney in Brooklyn and the dean of students at Harvard Law School — has been hired as the first chief diversity officer of the Metropolitan Opera, the largest performing arts institution in the United States.

Her appointment, which the Met announced on Monday, is something of a corrective to the company’s nearly 140-year history and a response to the Black Lives Matter demonstrations that followed the killing of George Floyd in 2020. It’s also a conscious step toward inclusivity by a major player in an industry in which some Black singers, including Leontyne Price and Jessye Norman, have found stardom, but diversity has lagged in orchestras, staff and leadership.

Since last summer, cultural institutions across the country have made changes as the Black Lives Matter movement drew scrutiny to racial inequities in virtually every corner of the arts world. The Met was no exception: The company announced plans to open next season with Terence Blanchard’s “Fire Shut Up in My Bones,” its first opera by a Black composer, directed by James Robinson and Camille A. Brown, who will become the first Black director to lead a production on the Met’s main stage. It also named three composers of color — Valerie Coleman, Jessie Montgomery and Joel Thompson — to its commissioning program.

But to make broader changes at the Met, an institution with a long payroll and a budget in the hundreds of millions of dollars, the Met is turning to Ms. Sells. As a member of the senior management team, she will report to Peter Gelb, the general manager. The human resources department will be brought under her direction, and her purview will be broad: the Met in its entirety, including the board.

“Sometimes horrible events like the killing of George Floyd catalyze people, and they realize this is something we need to do — at the Met and across the arts,” Ms. Sells said in an interview about her plans to make the Met a more inclusive company that values the diversity of its staff and the audiences it serves.

Mr. Gelb described Ms. Sells as an “ideal” candidate. “Not only does she have a history of accomplishment, but she also has a knowledge of the performing arts, having been involved in them herself,” he said in an interview. “And she loves opera, which is definitely a plus.”

Ms. Sells began dancing as a 4-year-old in Cincinnati, an arts-rich city where she found herself both onstage and in the audience of the storied Music Hall, and where she saw a young Kathleen Battle sing as a student at the University of Cincinnati College-Conservatory of Music.

“It had been part of my growing up to experience art,” she said.

She later joined Arthur Mitchell’s company, Dance Theater of Harlem, then remained in New York to attend Barnard College and Columbia Law School. Ms. Sells described herself as “an affirmative action baby,” and said that as both a dancer and a law student she had encountered racism, both overt and insidious, that made her feel unwelcome.

Ms. Sells recalled, for instance, a judge in the mid-1980s who told her that witnesses had to wait outside the courtroom. She said that she was actually an assistant district attorney, and he replied, “Wow, things have changed.”

Diversity has been at the fore of her work as an administrator — at places including Columbia, the N.B.A. and eventually Harvard Law, where she has been the dean of students since 2015. Her mandate at the Met won’t be too far from that of Harvard, another institute often perceived as elite to the point of exclusivity.

“It’s not just that you want to get it right,” Ms. Sells said. “There are a lot of eyes on you, but it’s a huge opportunity to show the way, as well as learn from other organizations that don’t have as big a name, are not as well known, and help shine a light on that work and on them.”

She plans to start at the Met in late February. Among her early tasks will be to conceive a diversity, equity and inclusion plan that could be implemented across hiring, artistic planning and engagement; she will also examine structural inequities at the Met, and work with the marketing and development departments to broaden the company’s audience and donor base.

The Met has been shut down because of the pandemic since last March, and most of its workers have been furloughed without pay since April. It is facing a major labor dispute with its unions, as well as more than $150 million in lost revenue from the theater’s closure. But Mr. Gelb said that the company hopes to receive assistance for diversity-related costs from foundations.

What those costs are will become clearer as Ms. Sells settles into her new job. She said that she was ready, and motivated by the company’s recent recognition “of how structurally or historically the Met has not felt welcoming to people of color” and the range of possibilities for change.

“I truly believe,” Ms. Sells said, “that this is the Met’s moment.”