The Bonville–Courtenay feud of 1455 was a series of raids, sieges, and attacks between two major Devon families, the Courtenays and the Bonvilles, in south west England, in the mid-fifteenth century. One of many such aristocratic feuds of the time, it became entwined with national politics due to the political weight of the protagonists. The Courtenay earls of Devon were the traditional powerbrokers in the region, but by this time a local baronial family, the Bonvilles, had become more powerful and rivalled the Courtenays for royal patronage. Eventually this rivalry spilled over into physical violence, including social disorder, murder and siege.
The Bonville-Courtenay feud is often given as an example of the degree to which law and order and respect for the king had broken down in the provinces. As a result, modern historians have often considered it a cause of the later Wars of the Roses, and, indeed, the course of the feud often closely followed the sectarian politics of the day. The feud is perhaps most well known for culminating in an armed encounter at Clyst (called the fight, or sometimes the battle, of Clyst), near Exeter, which resulted in loss of life.
Clyst resulted in government intervention in the politics of the west country. This was unusual, as the government did not have a good track-record of settling local disputes among the nobility. However, it is likely that this was done for reasons of higher politics; Bonville was by 1455 a Yorkist, and the duke of York had been made Protector. Although in the short term it resulted in the earl of Devon's incarceration, it did not come to an effective end until the protagonists were all killed in the early years of the civil wars.
The mid-fifteenth century suffered greatly from the private feuds of the nobility, and the Wars of the Roses in general. Devonshire, whilst experiencing none of the pitched battles, was still ravaged by a private feud. This was between Thomas Courtenay, earl of Devon, whose family had been earls of that county since 1335 and Sir William, Lord Bonville. Their feud became inextricably tied to the national political scene, but originated in regional Devon society. In 2003, historian Martin Cherry agreed that the south west was to a great degree lawless at this time. However, he suggested that the Bonville-Courtenay feud, whilst being the most well-known, is not the sole example of political upheaval in the region, but was common throughout the century.