The Cathedral of St. Matthew the Apostle in Washington, D.C., most commonly known as St. Matthew's Cathedral, is the seat of the Archbishop of the Roman Catholic Archdiocese of Washington. As St. Matthew's Cathedral and Rectory, it has been listed on the National Register of Historic Places since 1974.

The cathedral is in downtown Washington at 1725 Rhode Island Avenue NW between Connecticut Avenue and 17th Street. The closest Metrorail station is Farragut North, on the Red Line. It is seven blocks north and two blocks west of the White House.

St. Matthew's is dedicated to the Matthew the Apostle, who among other things is the patron saint of civil servants, having himself been a tax collector. It was established in 1840 by pastor Father William Matthews and parochial vicar Father John Philip Donelan. The church was dedicated on November 1, 1840, though the structure had not yet been entirely completed. Originally located at 15th and H Streets, construction of the current church began in 1893, with the first Mass being celebrated June 2, 1895. Construction continued until 1913 when the church was dedicated. In 1939, it became the cathedral for the newly established Archdiocese of Washington.

The structure is constructed of red brick with sandstone and terra cotta trim in the Romanesque Revival style with Byzantine elements. Designed by architect C. Grant La Farge, it is in the shape of a Latin cross measuring 155 ft × 136 ft (47 m × 41 m) and seats about 1,200 persons. The interior is richly decorated in marble and semiprecious stones, notably a 35 ft (11 m) mosaic of Matthew behind the main altar by Edwin Blashfield. The cathedral is capped by an octagonal dome that extends 190 ft (58 m) above the nave and is capped by a cupola and crucifix that brings the total height to 200 ft (61 m). Both structural and decorative elements underwent extensive restoration between 2000 and September 21, 2003, the feast day of St. Matthew.

The first notable funeral Mass offered at St. Matthew's was for Manuel L. Quezon, the president of the Philippines, who died August 1, 1944, and was interred at Arlington National Cemetery until the end of World War II. In 1957, a Solemn Requiem Mass was offered at the cathedral for the funeral of Senator Joseph McCarthy; the liturgy was attended by 70 senators and hundreds of clergymen and it was filled to capacity.

The cathedral drew worldwide attention following the assassination of United States President John F. Kennedy on Friday, November 22, 1963, in Dallas, Texas. Richard, Cardinal Cushing, Archbishop of Boston and a Kennedy family friend, offered a recited (not sung) Pontifical Requiem Low Mass during the state funeral on Monday, November 25, 1963, which was followed by the procession to Arlington National Cemetery in Virginia for the burial.

Other notable events at the cathedral include a Mass celebrated by Pope John Paul II during his 1979 visit to Washington, D.C., and the 1997 funeral of U.S. Supreme Court Associate Justice William J. Brennan, Jr.

The cathedral was the site of a Lutheran funeral service for Chief Justice William Rehnquist on September 7, 2005.

St. Matthew's is the location for one of the most famous Red Masses in the world. Each year on the day before the term of the Supreme Court of the United States begins, Mass is celebrated to request guidance from the Holy Spirit for the legal profession. Owing to the cathedral's location in the nation's capital, the Justices of the Supreme Court, members of Congress and the Cabinet, and many other dignitaries (including, at times, the President of the United States) attend the Mass. Dwight Eisenhower became the first to attend as president in 1954; Harry Truman attended nine years earlier, but as vice president.

In 2020, at the start of the COVID-19 pandemic, the cathedral hosted an archdiocesan Easter Mass via livestream. The Mass, live-streamed by The Roman Catholic Archdiocese of Washington and televised by EWTN, was celebrated by archbishop Wilton Gregory with no members of the faithful present due to COVID-19 restrictions.

Prior to the inauguration of Joe Biden as the 46th President of the United States he, along with Senate Majority Leader Mitch McConnell, Senate Minority Leader Chuck Schumer, Speaker of the United States House of Representatives Nancy Pelosi and House Minority Leader Kevin McCarthy attended Mass at the church. Shortly after this Mass, the United States Conference of Catholic Bishops voted to require that Communion be denied to any politician who supports abortion, including President Biden, with 73 percent in favor and 24 percent opposed.

Near the entry of the St. Francis Chapel is a burial crypt with eight tombs intended for Washington's archbishops. Three former archbishops, Patrick Cardinal O’Boyle, William Cardinal Baum, and James Cardinal Hickey, are interred here.

• List of Catholic cathedrals in the United States
• List of cathedrals in the United States

• Philibert, Helene, Philibert, Estelle, Philibert, Imogene (1940). Saint Matthew's of Washington. Baltimore, MD: A. Hoen & Co.

• Official Cathedral Site
• Roman Catholic Archdiocese of Washington Official Site
• Marble plaque in front of the sanctuary gates commemorates President John F. Kennedy's funeral Mass Archived 2010-04-02 at the Wayback Machine
• Cathedral of St Matthew the Apostle: Photo Gallery by The Catholic Photographer Archived 2015-02-12 at the Wayback Machine