Thomas Becket, Archbishop of Canterbury and former close friend of Henry II, was murdered in Canterbury Cathedral on 29 December 1170 by four knights acting on the king's frustrated words. The killing shocked Christian Europe and transformed Becket almost instantly into a martyr and saint. Pope Alexander III canonised him in 1173, and Canterbury became one of the most important pilgrimage sites in Europe within a few years of his death. Henry II performed public penance at Becket's tomb in 1174, acknowledging the authority of the Church in a defining moment of the medieval struggle between royal and ecclesiastical power.

Becket's martyrdom generated an immediate and sustained literary response: hagiographies, Latin hymns, French verse lives (including Guernes de Pont-Sainte-Maxence's celebrated verse life), and vernacular laments appeared within years of his death. Most enduringly, he gave Chaucer the destination and moral framework for The Canterbury Tales, one of the greatest poems in English. T.S. Eliot's Murder in the Cathedral (1935) returned to the event to interrogate the nature of sainthood and political martyrdom.