What was Mendel's religious name after becoming a monk?

Mendel’s religious name after becoming a monk was Gregor. Born Johann Mendel in 1822, he entered the Augustinian monastery of St. Thomas in Brno in 1843 and adopted the monastic name Gregor, later commonly appearing as Gregor Johann Mendel.

The monastery gave Mendel more than a religious home. Its abbot, Cyril Napp, recognized his intellectual ability and supported further study. Mendel was ordained a priest in 1847, but his interests in mathematics, natural science, and teaching remained central to his life.

“Johann” was not discarded entirely: it remained part of his full name. That is why historical references may use either Johann Mendel for his early life or Gregor Johann Mendel for his later scientific career. The name “Augustin” can also cause confusion because Mendel belonged to the Order of St. Augustine, but it was not the name he adopted as a monk.