Simonides lived in the 6th and 5th Centuries B.C. and was known throughout the Greek world for his lyric poetry and for a strategy of memory retention. He is also said to have invented some letters of the alphabet.

Simonides was born about 556 B.C. in the town of Iulis, on the island of Ceos (which is now Kea), an island in the Cyclades, in which also was Delos, home of the Delian League. Little is known of his early life there. He moved to Athens at some point and became popular for his poetry.

He became known for his skill in composing epitaphs for fallen soldiers and victory odes for athletes who won competitions. Possibly his most famous work came after the famed Greek victory at the Battle of Marathon. He wrote both an epigram honoring the Greeks who died in the battle and a collection of commemorative verse celebrating the heroes who survived. He also wrote poems focusing on other battles of the Greco-Persian Wars, among them Artemisium, Plataea, and Salamis. Another of his famous works was in honor of Leonidas and the Spartans who fell at Thermopylae.

Two other types of writing for which he was well known were the encomium, a specific kind of writing whose purpose was to praise a person or thing, and the dithyramb, a set of lyrics sung in honor of the god Dionysus. One later source wrote that Simonides won 57 dithyramb competitions.

Simonides also developed a strategy for remembering things based on association with images and places. This method has sometimes been called "the memory palace."

He is mentioned in writings by other Greeks, notably Aristophanes and Aristotle and Plato, and is portrayed as either a wise man or a miser. The Roman Plutarch had this to say: "Simonides calls painting silent poetry and poetry painting that speaks."

According to the Suda, a Byzantine encyclopedia, Simonides added four letters to the Greek alphabet.

Simonides died about 468 B.C. in Acragas, which is now Agrigento, in Sicily. Not much of what he wrote survives. His nephew Bacchylides was also a well-known lyric poet.