count of Anjou (1040–60), whose territorial ambitions, though making him troublesome to his father, Fulk III Nerra, resulted in the further expansion of Angevin lands after his father's death. (Geoffrey's byname, Martel, means “the Hammer.”)

In 1032 Geoffrey married Agnes, widow of William V the Great, Duke of Aquitaine. Claiming Aquitaine for Agnes' children by William the Great, Geoffrey attacked William's son by an earlier marriage, William the Fat, who had succeeded his father as duke. Fulk, who was William's vassal, sided with him against Geoffrey. Geoffrey in turn tried to seize his father's lands while the latter was on a pilgrimage to the Holy Land (1039); Fulk pardoned him only after forcing him to suffer great humiliation.

When Fulk died in 1040, Geoffrey embarked on a policy of expansion that at various times during the next 20 years brought him into conflict with Thibaut III, Count of Blois and Champagne; Henry I, king of France; and William I, Duke of Normandy; he extended his lands to include Touraine and a large part of Maine.