Plutarch's Parallel Lives is a series of biographies, arranged in pairs, illuminating virtues and vices. The surviving Lives contain 23 pairs, each with a Greek and a Roman Life, and 4 unpaired Lives.

As explained in the opening of his Life of Alexander, Plutarch wasn't concerned with history so much as the influence of character on life and destiny. While he sometimes barely touched on great events, he devoted much space to anecdotes and incidental triviality, often revealing more about his subjects than their famous accomplishments.

He sought to provide rounded portraits, likening his craft to painting. Indeed, he went to great, often tenuous, lengths to draw parallels between physical appearance and character.

Amongst the earliest moral philosophers, some of the Lives, like those of Heracles, Philip II of Macedon, and Scipio Africanus, are lost. Many remaining Lives are truncated, contain lacunae, or have been tampered with. Extant are those on Solon, Themistocles, Aristides, Pericles, Alcibiades, Nicias, Demosthenes, Pelopidas, Philopoemen, Timoleon, Dion of Syracuse, Alexander the Great, Pyrrhus of Epirus, Romulus, Numa Pompilius, Coriolanus, Theseus, Aemilius Paullus, Tiberius Gracchus, Gaius Gracchus, Gaius Marius, Sulla, Sertorius, Lucullus, Pompey, Julius Caesar, Cicero, Cato the Younger, Mark Antony, and Marcus Junius Brutus.