In the mythology of William Blake, Urizen is the embodiment of conventional reason and law. He is usually depicted as a bearded old man; he sometimes bears architect's tools, to create and constrain the universe; or nets, with which he ensnares people in webs of law and conventional society. Originally, Urizen represented one half of a two-part system, with him representing reason and Los, his opposition, representing imagination. In Blake's reworking of his mythic system, Urizen is one of the four Zoas that result from the division of the primordial man, Albion, and he continues to represent reason. He has an Emanation, or paired female equivalent, Ahania, who stands for Pleasure. In Blake's myth, Urizen is joined by many daughters with three representing aspects of the body. He is also joined by many sons, with four representing the four elements. These sons join in rebellion against their father but are later united in the Last Judgment. In many of Blake's books, Urizen is seen with four books that represent the various laws that he places upon humanity.

William Blake was an English poet, painter, and printmaker. Largely unrecognised during his life, Blake is now considered a seminal figure in the history of the poetry and visual art of the Romantic Age. What he called his "prophetic works" were said by 20th-century critic Northrop Frye to form "what is in proportion to its merits the least read body of poetry in the English language". While he lived in London his entire life, except for three years spent in Felpham, he produced a diverse and symbolically rich collection of works, which embraced the imagination as "the body of God", or "human existence itself".