John Joseph Glennon (June 14, 1862 – March 9, 1946) was a prelate of the Roman Catholic Church, serving as Archbishop of St. Louis from 1903 until his death in 1946.

He accepted an invitation from Bishop John Joseph Hogan in 1882 to join the newly erected Diocese of Kansas City in the United States.

The St. Louis chapter of the Midwest Clergy Conference on Negro Welfare, formed locally in 1938, pushed the all-female Webster College to integrate first.

The Pittsburgh Courier, an African-American newspaper with national circulation, discovered Glennon's intervention and ran a front-page feature on the Webster incident.

In response, Fr Claude Heithaus, SJ, professor of Classical Archaeology at Saint Louis University (SLU), delivered an angry sermon accusing his own institution of immoral behavior in its segregation policies.

SLU began admitting African American students that summer when its president, Fr Patrick Holloran, SJ, managed to secure approval from the reluctant Glennon.

[2] He originally thought himself too old to make the journey to Rome,[4] but eventually joined fellow Cardinals-elect Francis Spellman and Thomas Tien Ken-sin on their flight, during which time Glennon contracted a cold from which he did not recover.

During the return trip to the United States, Glennon stopped in his native Ireland, where he was received by President Seán T. O'Kelly and Taoiseach Éamon de Valera.