Mumadona Dias, or Muniadomna Díaz, Countess of Portugal in the 10th century, ruling between c. 924 - c. 950. She was daughter of Count Diogo Fernandes and of countess Onega.
Celebrated, rich and the most powerful woman in the Northwest of the Iberian peninsula, she has been commemorated by several Portuguese cities.
In c. 926 Mumadona was already married to Count Hermenegildo González. She governed the county alone after her husband's death in c. 928. She left it in the ownership of countless domains, in an area that coincided reasonably with zones that would integrate the back counties of Portucale and of Coimbra.
Those domains were divided in July 950 among her six children, giving Gonzalo Menéndez the county of Portucale. In 950 or 951, with divine inspiration, she founded, on her property in Vimaranes, a monastery under São Mamede's invocation (Mosteiro of São Mamede or Mosteiro of Guimarães). Later she professed her vows there. To protect this monastery and its people from Viking raids, she initiated the construction of the Castle of Guimarães, in the shade of which Guimarães' burgh was developed. Eventually this became the headquarters of the court of the counts of Portucale.
The testamentary document in which she makes the donation of her domains, cattle, incomes, religious objects and books to Guimarães monastery, dated of January 26 959, was important for verifying the existence of several castles and villages in the region.