Matilda married Geoffrey, Count of Anjou, at Le Mans, forging the Angevin alliance behind the future Plantagenet dynasty.
On 17 June 1128, Matilda married Geoffrey of Anjou, known as 'Geoffrey the Fair' or 'Plantagenet' for the sprig of broom blossom (planta genista) he reportedly wore, in a ceremony at Le Mans. The marriage was arranged by Henry I to secure the vulnerable southern border of Normandy through an alliance with the powerful County of Anjou, historically a rival power.
The match was unpopular with Matilda, who as a former empress considered the much younger count of comparatively modest rank beneath her former status, and the marriage was reportedly strained in its early years, with periods of separation. Nonetheless, it proved to be the single most consequential union of the entire succession crisis: it produced three sons, the eldest of whom, born in 1133, would become King Henry II of England, founder of the Plantagenet dynasty that ruled England for over three centuries.
Diplomatically, the marriage extended Matilda's power base onto the continent and gave her the military resources of Anjou to draw upon during her later campaign against King Stephen. Though the marriage itself lacked initial personal warmth, it fundamentally reshaped the political map of England and France, laying the groundwork for the vast Angevin Empire her son would rule.