Matilda (or Maud -- the French form of the name) was the daughter of Henry I of England, and his wife Maud/Matilda of Scotland, herself daughter of Malcolm III and Margaret, daughter of Edward Atheling.
She was christened Adelaide, but adopted the name of Matilda/Maud on her marriage to Henry V, the Holy Roman Emperor, in 1114, aged 12. The marriage was childless and after 11 years Henry died. She returned to England where her father arranged a new marriage for her, with Geoffrey of Anjou (nicknamed Plantagenent), he being all of 13 years old. They were to have three sons, Henry, who would later become Henry II of England, Geoffrey, Count of Nantes, and William, Count of Poitou.
Henry I selected Matilda as his heir, having no sons, and had the English baronage swear to support her. Unfortunately, when he died in 1135, Stephen of Blois was positioned just across the English Channel, and he rushed over to Winchester, where his brother was the bishop as well as guardian of the royal treasury, and had himself declared king (he had a claim to the throne through his mother, William the Conqueror's daughter, Adela of Normandy; additionally, the English did not want Geoffrey of Anjou as king, and had no remembrance of a woman as Queen regnant).
When Stephen made his move, it was winter and Matilda was pregnant with her third son, which delayed her making an immediate response. Over the next three years Count Geoffrey attempted to pursue the matter by attacking castles held by English nobles in Normandy. Meanwhile, Stephen had begun to lose the support of some of the English nobility and offended the clergy over a number of matters. Most especially he angered his brother Bishop Henry by not supporting him for Archbishop of Canterbury when the see became vacant. Deeming it the right moment to return, Matilda and Robert of Gloucester landed a modest force near Arundel castle in September 1139. After over a year spent gathering support, Robert of Gloucester's army was able to meet Stephen in battle at Lincoln on 2 February 1141, where Stephen was defeated and captured. With the support of Bishop Henry, Matilda was shortly declared "Lady of the English" and was about to be crowned as Queen at Westminster when the citizens of London rose against her and she and all her court were forced to flee into the countryside. Several months of intense intermittent fighting followed, during which Matilda's support melted away, in part because of her high-handedness and temper. After several setbacks, as well as the town of Winchester being burnt by an exchange of fire arrows, Matilda and her forces were routed out of Winchester in mid-September 1141. Though she escaped--being forced at one point to ride astride--Robert of Gloucester and a number of her other supporters were captured, resulting in an exchange of Gloucester for Stephen a few weeks later. Though the fighting continued intermittently over the next several years, including another dramatic escape from a siege at Oxford for Matilda, concealed in a white cloak to blend in with the snow-covered countryside, it was clear that her opportunity to become Queen had been lost and attention now focused on securing the realm for her son Henry when he should be old enough. When Robert of Gloucester died in 1147, Matilda's position became even more untenable and she soon after returned to France.
However, her son Henry had grown into a fine man, and when, in 1153, Stephen's heir, Eustace, died, Henry crossed the Channel himself, and Stephen, aged and grieving over the deaths of his son and wife, agreed, by the Treaty of Wallingford, that on his death Henry should succeed. Stephen lived another year, and Henry took the throne, as England's first Plantagenet king.
His mother remained in France, and died in 1167, the daughter, wife and mother of Henry, as it were.