Nicolaus Aloysius Gallagher (February 19, 1846 – January 21, 1918) was an American prelate of the Roman Catholic Church.

At age 10, he was tutored by a priest in Coshocton, Ohio, in English, grammar, Latin, and Greek for six years.

[1] In 1862, Gallagner entered Mount St. Mary's of the West Seminary in Cincinnati, Ohio, where he studied philosophy and theology.

[1] In 1881, Bishop Claude Marie Dubuis of the Diocese of Galveston returned to his home in France due to poor health.

After the 1900 Galveston hurricane devastated the city, Gallagher rebuilt all the destroyed Catholic institutions.