Dicaearchus (also correct in English Dicearchos, Dicearchus or Dikæarchus) (Greek Dixaiarxos) (circa 350 BC - circa 285 BC) was a Greek philosopher, cartographer, geographer, mathematician and author.

He was born in Messine (also Messana, Messene; present-day Messina).

Dicaearchus was Aristotle's student in Lyceum. His work is almost lost. He made geometric constructions of a hyperbola and a parabola and worked mainly in the field of cartography, where he was among the first to use geographical coordinates.