Papula of Gaul|
(6th - 7th century) France
The virgin Papula, is said to have donned male attire and fled to a monastery to escape her worldly parents, to have been chosen as abbot over the men, and to have worked miracles from her tomb after her death (when her true sex was at last discovered).
Source: Saints' Lives and the Rhetoric of Gender: Male and Female in Merovingian Hagiography, By John Kitchen. Oxford University Press