Diogenes Laertius was a biographer of Greek philosophers, likely active in the first half of the 3rd century CE. His name suggests origins in Laerte in Cilicia or Crete, though this remains uncertain. He dedicated his major work to a woman interested in Plato, indicating he moved within educated circles.

His extant work is the Lives and Opinions of Eminent Philosophers, a ten-book compilation. He also wrote the Pammetros, a lost collection of poems by philosophers. Diogenes Laertius is a principal source for the history of ancient Greek philosophy. His compilation preserves biographies, doctrines, and anecdotes for over eighty philosophers, drawing from many now-lost sources.

While criticized for a lack of critical analysis, his work is indispensable, especially for understanding Hellenistic schools like the Epicureans, whose three surviving letters he alone preserved.