Diogenes Laërtius (dĪŏjˈənēz lāörˈshēəs) [key], fl. early 3d cent., Greek biographer. Extant is a work in 10 books on the lives and opinions of the philosophers from Thales to Epicurus, with whole books devoted to Plato and Epicurus. His work is an invaluable source of history.
See his Lives of Eminent Philosophers, tr. by R. D. Hicks (1925, repr. 1979–80).