Timaeus of Tauromenium was a Greek historian born around 350 BCE in Sicily. He was the son of Andromachus, the founder of the city of Tauromenium. Exiled by the tyrant Agathocles around 317 or 316 BCE, he spent at least fifty years in Athens. There he studied under Philiscus of Miletus and composed his historical works. He died at an advanced age, possibly around 260 BCE.

His major work was the Histories, also known as the Sicilian History, a comprehensive account of Sicily and the western Greeks from mythical times to at least 289 BCE. He also authored the Olympionikai, a chronological list of Olympic victors, and a work titled On Pyrrhus, concerning the campaigns of Pyrrhus of Epirus. All of his writings survive only in fragments preserved by later authors such as Polybius and Diodorus Siculus.

Timaeus was the preeminent historian of the western Greeks before Polybius, and his work became the standard authority for the region. He pioneered important methodological advances, most notably using the list of Olympic victors to establish a unified chronology for Greek history. His reputation was controversial. Polybius criticized him harshly for pedantry and inexperience in military and political matters, while other historians, such as Dionysius of Halicarnassus, acknowledged his wide learning despite his often polemical style.