McElroy, 70, replaces Cardinal Wilton Gregory, who at 77 is two years beyond the normal retirement age for bishops and steps down after having navigated the fallout of a new eruption of the clergy sexual abuse crisis.
The Vatican announced the appointment Monday, the Catholic feast of the Epiphany, in a bulletin that flagged another important appointment. Francis named Italian Sister Simona Brambilla the first-ever woman to head a Vatican dicastery, in this case the one responsible for religious orders.
MORE: Pope Francis has named the first woman to head a major Vatican office
Francis, who was elected pope on a mandate of reform, has long had his eye on McElroy, making him bishop of San Diego in 2015 and then elevating him as a cardinal in 2022.
McElroy has been one of a minority of U.S. bishops to harshly criticize the campaign to exclude Catholic politicians who support abortion rights from Communion, a campaign Francis has publicly criticized by insisting that bishops must be pastors, not politicians.
He has also questioned why the U.S. bishops' conference, which has leaned conservative in its leadership, consistently insists on identifying abortion as its "preeminent" priority. He has questioned why greater prominence was not given to issues such as racism, poverty, immigration and climate change.
He has also expressed support for LGBTQ+ youth and denounced the bullying often directed at them, further aligning himself with Francis' priorities as pope.
"McElroy is competent, kind, empathetic, and willing to fight on the side of the vulnerable," said Natalia Imperatori-Lee, chairperson of the religion and philosophy department at Manhattan University. She said his nomination was particularly timely given the polarization in the U.S.
"McElroy has experience leading a diocese marked by diversity and challenges, and I can't think of a bigger challenge than to be so close to the seat of the U.S. government in 2025," she said in an email.
The Rev. James Martin, a Jesuit known for his outreach to the LGBTQ+ community, also praised the appointment, calling McElroy "one of the brightest and most capable clerics" in the U.S. church.
McElroy, a graduate Harvard University with a masters in history from Stanford University, is a native of San Francisco and had ministered there until Francis moved him to San Diego.
"With doctorates in both theology and political science, and experience as bishop of San Diego, Cardinal McElroy is both smart and pastoral," Martin said in a social media post.
McElroy's appointment to Washington comes just a few weeks after Trump, who takes office Jan. 20, nominated Brian Burch as U.S. ambassador to the Holy See. Burch, president and co-founder of the advocacy group CatholicVote, has criticized Francis and some of his policies on social media.
Francis made the appointment ahead of his final meeting with President Joe Biden, who is making a last foreign trip to Italy this week. Biden emerged from a 2021 meeting with Francis by saying the pope told him to continue receiving Communion despite his position on abortion.
He later received the sacrament at a Rome church.
The Archdiocese of Washington includes the District of Columbia and five Maryland counties of Montgomery, Prince George's, St. Mary's, Calvert and Charles. It has a total population of 3,050,847, of which 671,187 are Catholic.
Its outgoing archbishop, Gregory, took over in 2019 at a time of turmoil for one of the nation's most important archdioceses. Its two previous leaders, ex-Cardinal Theodore McCarrick and Cardinal Donald Wuerl, were caught up in a new wave of the long-running clerical sexual abuse scandal.
Wuerl stepped down after he lost the trust of his flock, and McCarrick was defrocked.
Francis not only tapped Gregory to lead but then made him a prince of the church in 2020, making him the first Black American cardinal in the process.