This thesis uses the existing evidence relating to the de Bohun family, earls of Hereford and Essex, to examine the development of the dynastic sense of identity and pious practices of the nobility of thirteenth and fourteenth century England. The thesis analyses the existing evidence for the family over several generations, starting at the time the first Humphrey de Bohun arrived in England in 1066 with William the Conqueror and ending with the death of the family’s last co-heiress, Eleanor de Bohun, in 1399. First, it explores the royal service, marital alliances and extraneous, often fortuitous, circumstances that led to the de Bohuns’ accumulation of titles and lands over three and a half centuries. Second, it focuses on the evolution of the family's dynastic identity and the importance placed on lineage and family memory both by individual family members and by the family's descendants after the family's failure in the male line. Finally, the thesis examines the evidence of wills and religious and administrative records to gain insight into the family's crusading links, its religious patronage, and the piety exercised by individual family members as a means of justifying their noble status and obtaining divine protection for themselves and their family in life and after death.