Hesychius of Miletus the Illustrious was a Greek historian and biographer of the 6th century CE, active during the reign of Emperor Justinian I. His epithet “the Illustrious” indicates he held high rank, likely as a state official. A native of Miletus, he was the son of an advocate and father of the sophist John of Miletus. The Suda records that he taught in Constantinople, placing him within the capital’s intellectual and administrative circles.

His works, known primarily from the Suda, survive only in fragments. They include a World History, covering the origins of Constantinople to 518 CE; a History of the Reign of Justin I and Justinian I, covering 518–527 CE; a biographical dictionary titled On Famous Men of Learning, arranged by genre, which served as a major source for the Suda itself; and a Roman and General History, a six-book chronicle from the Assyrian king Belus to 518 CE.

Hesychius was a key compiler and transmitter of knowledge. His biographical dictionary was foundational for later Byzantine lexicography, while his historical works provided contemporary accounts of the early 6th century. His writings represent the secular Greek scholarly tradition during the age of Justinian.