Thomas Sebastian Byrne (July 28, 1841 – September 4, 1923) was an American Roman Catholic clergyman who served as the fifth Bishop of Nashville, Tennessee.
Byrne was born in Hamilton, Ohio, and prepared for the priesthood at St. Thomas Seminary in Bardstown, Kentucky; Mount St. Mary's Seminary of the West in Cincinnati; and the Pontifical North American College in Rome. He was ordained a priest on May 22, 1869, and on his return to the United States he became a member of the faculty of Mount St. Mary's in Cincinnati, of which institution he later became rector.
Appointed the fifth Bishop of Nashville on May 10, 1894, Byrne was consecrated by Archbishop William Henry Elder on the following July 25. He relieved the diocese of its debts, increased the number of priests and parishes, and began a building program. The new Cathedral with its school and rectory were also constructed. Many new charitable and educational institutions founded as well.
He died at age 82.