Plutarch's Lives of the Noble Greeks and Romans, commonly called Parallel Lives or Plutarch's Lives, is a series of 48 biographies of famous men, arranged in pairs to illuminate their common moral virtues or failings, probably written at the beginning of the second century AD. The surviving Parallel Lives (Greek: Βίοι Παράλληλοι, Bíoi Parállēloi) comprises 23 pairs of biographies, each pair consisting of one Greek and one Roman of similar destiny, such as Alexander the Great and Julius Caesar, or Demosthenes and Cicero. It is a work of considerable importance, not only as a source of information about the individuals described, but also about the times in which they lived.
Parallel Lives was Plutarch's second set of biographical works, following the Lives of the Roman Emperors from Augustus to Vitellius. Of these, only the Lives of Galba and Otho survive.
As he explains in the first paragraph of his Life of Alexander, Plutarch was not concerned with writing histories, but with exploring the influence of character, good or bad, on the lives and destinies of famous men. He wished to prove that the more remote past of Greece could show its men of action and achievement as well as the nearer, and therefore more impressive, past of Rome. His interest was primarily ethical, although the Lives has significant historical value as well. The Lives was published by Plutarch late in his life after his return to Chaeronea and, if one may judge from the long lists of authorities given, it must have taken many years to compile.
The chief manuscripts of the Lives date from the 10th and 11th centuries, and the first printed edition appeared in Rome in 1470. Thomas North's 1579 English translation was an important source-material for Shakespeare. Jacob Tonson printed several editions of the Lives in English in the late 17th century, beginning with a five-volume set printed in 1688, with subsequent editions printed in 1693, 1702, 1716, and 1727.