President-elect Donald J. Trump said on Monday that he would nominate Harmeet K. Dhillon, a California lawyer who has long championed Mr. Trump in public, in court cases and on social media, to run the Justice Department’s Civil Rights Division.

In declaring his choice on social media, Mr. Trump said Ms. Dhillon “has stood up consistently to protect our cherished civil liberties.” He praised her legal work targeting social media companies, restrictions on religious gatherings during the pandemic and “corporations who use woke policies to discriminate against their workers.”

Ms. Dhillon has been a conservative activist so devoted to Mr. Trump that she was willing to attack not only Democrats but also fellow Republicans, including her ultimately unsuccessful challenge last year to the chairwoman of the Republican National Committee at the time.

She was also the co-chairwoman in 2020 of a group, Lawyers for Trump, that challenged the results of that year’s presidential election.

It is not unusual for Republican administrations to significantly scale back the work in the Civil Rights Division. In Ms. Dhillon, however, Mr. Trump has chosen a lawyer active in the culture wars whose firm specializes in championing the right’s causes.

“I’m extremely honored by President Trump’s nomination to assist with our nation’s civil rights agenda,” Ms. Dhillon posted on social media. “It has been my dream to be able to serve our great country, and I am so excited to be part of an incredible team of lawyers led by” Pam Bondi, Mr. Trump’s choice for attorney general.

The division, which enforces voting rights laws, investigates police departments and brings charges for violations of people’s civil rights, is spending the final days of the Biden administration finishing as much work as possible on cases involving patterns or practices of police misconduct.

Earlier on Monday, the division announced findings highly critical of the police department in Worcester, Mass. Such findings, however, may not amount to much, given that those investigations will soon be handed over to the Trump administration.

During the first Trump administration, the Justice Department walked away from several high-profile cases involving misconduct by major city police departments, and lawyers who specialize in such cases have said they expect the second Trump administration to do much the same.