Leofric was the son of Ealdorman Leofwine of the Hwicce, who died c. 1023. Leofric's elder brother Northman was killed in 1017, in the losing battles against Cnut.
The victorious Cnut divided England into four great provinces: Wessex, East Anglia, Mercia and Northumbria each of which he eventually placed under the control of an earl (a title new to the English, replacing the Anglo-Saxon "ealdorman"). Mercia he initially left in the hands of Eadric Streona, who had been Ealdorman of Mercia since 1007, but Eadric was killed later in the same year of 1017.
Mercia may have been given to Leofric immediately after that. He had certainly become Earl of Mercia by the 1030s. This made him one of the most powerful men in the land, second only to Earl Godwin of Wessex among the mighty earls. He may have had some connection by marriage with Ælfgifu of Northampton, the first wife of Cnut. That might help to explain why he supported her son Harold Harefoot against Harthacanute, Cnut's son by Emma, when Cnut died in 1035.
However Harold died in 1040 and was succeeded by Harthacanute, who made himself unpopular with heavy taxation in his short reign. Two of his tax-collectors were killed at Worcester by angry locals. The king was so enraged by this that in 1041 he ordered Leofric and his other earls to plunder and burn the city, and lay waste the whole area.This command must have sorely tested Leofric. Worcester was the cathedral city of the Hwicce, his people.
When Harthacanute died suddenly in 1042, he was succeeded by his half-brother Edward the Confessor. Leofric loyally supported Edward when he came under threat at Gloucester from Earl Godwin in 1051. Leofric and Earl Siward of Northumbria gathered a great army to meet that of Godwin. Wise heads counselled that battle would be folly, with the flower of England on both sides. Their loss would leave England open to its enemies. So the issue was resolved by less bloody means. Earl Godwin and his family were outlawed for a time.
Earl Leofric's power was then at its height. But in 1055 his son Ælfgar was outlawed, "without any fault", says the Anglo-Saxon Chronicle. He raised an army in Ireland and Wales and brought it to Hereford, where he clashed with the army of Earl Ralph of Herefordshire and severely damaged the town. The Anglo-Saxon Chronicle wryly comments "And then when they had done most harm, it was decided to reinstate Earl Ælfgar".
Leofric died "at a good old age" in 1057 at his estate at Kings Bromley in Staffordshire. According to the Anglo-Saxon Chronicle, he died on 30 September, but the chronicler of Worcester gives the date as 31 August. Both agree that he was buried at Coventry.
Leofric used a double-headed eagle as his personal device, and this has been adopted by various units of the British Army as a symbol for Mercia.
Earl Leofric and Godiva were noted for great generosity to religious houses. In 1043 he founded and endowed a Benedictine monastery at Coventry. John of Worcester tells us that "He and his wife, the noble Countess Godgifu, a worshipper of God and devout lover of St Mary ever-virgin, built the monastery there from the foundations out of their own patrimony, and endowed it adequately with lands and made it so rich in various ornaments that in no monastery in England might be found the abundance of gold, silver, gems and precious stones that was at that time in its possession."
In the 1050s Leofric and Godiva appear jointly in the grant of land to the monastery of St Mary, Worcester, and the endowment of the minister at Stow St Mary, Lincolnshire. She and her husband are commemorated as benefactors of other monasteries at Leominster, Chester, Much Wenlock, and Evesham.
Apart from Northman, killed in 1017, Leofric had at least two other brothers. Edwin was killed in battle by Gruffydd ap Llywelyn in 1039. Godwine died some time before 1057.
Leofric may have married more than once. His famous wife Godiva survived him and may have been a second or later wife. Since there is some question about the date of marriage for Leofric and Godgifu, it is not clear that she was the mother of Ælfgar, Leofric's only known child. If Godiva was married to Earl Leofric only in 1040, she could not have been the mother of Ælfgar (whose own children were born in that decade or earlier). If she was married earlier (as early as 1017, as some sources claim), she could have been Ælfgar's mother.
Ælfgar succeeded Leofric as Earl of Mercia.