Mathilda was born around 895 to the Westphalian Saxon count Dietrich and his wife Reinhild — descended from the legendary Saxon hero Widukind (the Saxon resistance leader against Charlemagne, baptized in 785).
Around 909, at the age of 14, she was married to Henry, Duke of Saxony (the future Henry I the Fowler) — a dynastic marriage uniting the Saxon and Westphalian Carolingian-aristocratic kindreds. In 919, with the death of Conrad I, Henry was elected King of the East Franks (Germany) — making Mathilda the queen of the nascent East Frankish (German) kingdom.
She and Henry produced five royal children: Otto I the Great (the future Holy Roman Emperor, 936–973), Henry I the Quarrelsome (Duke of Bavaria), Bruno the Great (Archbishop of Cologne, saint), Gerberga of Saxony (Queen of West Francia, mother of King Lothair), and Hedwig of Saxony (Duchess of the Franks, mother of the Capetian dynasty's founder Hugh Capet). The Saxon royal dynasty that Mathilda bore would shape the entire 10th–11th-century European political order.
On Henry's death in 936, the political tension between her sons Otto and Henry over the succession — and Mathilda's personal preference for the younger Henry — produced political-familial conflict. Otto was elected king (and later crowned Emperor in 962). Otto's queen Edith (daughter of Edward the Elder of England) was Mathilda's daughter-in-law; their relationship was complex, with Mathilda undergoing brief political exile from the court before being restored.
In her widowhood, Mathilda founded multiple monastic communities — most the Quedlinburg Abbey in Saxony (936, on the site of Henry's royal palace) and the Nordhausen Abbey, placing them under the governance of her granddaughters and royal kinswomen. The Quedlinburg Abbey became the principal Ottonian royal women's-monastic foundation, housing the royal Ottonian nuns and the royal genealogical-and-liturgical traditions.
She died at Quedlinburg on March 14, 968, having outlived her husband by thirty-two years.