Linear B tablets preserve the personal name Achilleus in the forms a-ki-re-u and a-ki-re-we (the latter a dative). The name became increasingly popular after the seventh century BCE and was also adapted into the female form Achilleía in fourth-century BCE Attica.

Achilles's name can be analyzed as a combination of áchos (distress, pain, sorrow, grief) and laós (people, soldiers, nation), yielding a proto-form meaning 'he who has the people distressed' or 'he whose people have distress.' The grief of the people recurs throughout the Iliad and frequently in Achilles's own speeches, creating an ironic contrast with the conventional view of him as a hero of kléos (glory in war). Some scholars instead propose the name may be a loan word from a pre-Greek language, noting Achilles's descent from the Nereid Thetis and the similarity of his name to river deities such as Acheron and Achelous, suggesting possible origins as an old water divinity.

Achilles was known by multiple appellations, including Pyrisous ('saved from the fire'), Aeacides (from his grandfather Aeacus), Aspetos ('inimitable' or 'vast', his name in Epirus), Larissaeus, Ligyron (his original name), Nereius (from his mother Thetis), Pelides (from his father Peleus), Phthius (from his birthplace Phthia), and Podarkes ('swift-footed').

Achilles was the son of Thetis, a Nereid and daughter of the Old Man of the Sea, and Peleus, king of the Myrmidons. Both Zeus and Poseidon had sought Thetis's hand until Prometheus warned Zeus of a prophecy — originally from Themis, goddess of divine law — that Thetis would bear a son greater than his father. Both gods withdrew their pursuit, and Thetis was married to Peleus. An alternative account in the Argonautica holds that Thetis resisted Zeus's advances out of loyalty to Hera, who had raised her, and that Zeus, enraged, decreed she would never marry an immortal.

According to Statius's Achilleid and lost earlier sources, when Achilles was born Thetis attempted to make him immortal by dipping him in the river Styx, but held him by his left heel, leaving that part vulnerable. In an alternate version she anointed the boy with ambrosia and placed him atop a fire to burn away his mortal parts, but Peleus interrupted her and she abandoned them both in rage. Notably, earlier sources before Statius make no reference to universal invulnerability: the Iliad itself describes Achilles being wounded (in Book 21 the Paeonian hero Asteropaios grazes his elbow with a spear, 'drawing a spurt of blood'), and the Epic Cycle poems describing his death contain no reference to a heel vulnerability.

Peleus entrusted Achilles to Chiron, the most righteous of the Centaurs, who lived on Mount Pelion; some accounts say his original name was 'Ligyron' and that Chiron renamed him Achilles. According to Homer, Achilles grew up in Phthia with his childhood companion Patroclus, and taught Patroclus what Chiron had taught him, including medicine. Thetis foretold that her son would either gain glory and die young or live a long, uneventful life in obscurity; Achilles chose the former and resolved to join the Trojan War.

In the Iliad Achilles is portrayed as tall and striking, with unmatched strength and appearance among the Greek warriors. Homer describes his hair with xanthḗ ('yellow', covering light shades from blond to auburn), Philostratus wrote that his eyes were amber and lion-like, and a later Latin account falsely attributed to Dares Phrygius describes him with 'a large chest, a fine mouth, and powerfully formed arms and legs' and 'long wavy chestnut-colored hair,' adding that he was 'mild in manner' but 'very fierce in battle.'

Some post-Homeric sources claim Thetis or Peleus hid the young Achilles, dressed as a girl, at the court of Lycomedes, king of Skyros, to keep him from war, where he lived among Lycomedes's daughters under names such as 'Pyrrha' (the red-haired girl). With Lycomedes's daughter Deidamia he fathered two sons, Neoptolemus and Oneiros. Learning from the prophet Calchas that Troy could not be taken without Achilles, Odysseus went to Skyros disguised as a peddler and placed a shield and spear among women's goods; when Achilles instantly seized the spear, Odysseus recognized him and convinced him to join the campaign.

According to the Iliad, Achilles arrived at Troy with 50 ships, each carrying 50 Myrmidons, and appointed five leaders over them: Menesthius, Eudorus, Peisander, Phoenix, and Alcimedon. Earlier in the war the Greeks accidentally landed in Mysia, where Achilles wounded its king Telephus with a wound that would not heal; an oracle declared 'he that wounded shall heal,' and Achilles later cured Telephus (with scrapings from his spear) so that he could guide the Greeks to Troy.

According to the Cypria, Achilles restrained the Achaeans from returning home, attacked the cattle of Aeneas, sacked neighbouring cities including Lyrnessus (where the Greeks captured Briseis), and killed Tenes, a son of Apollo, as well as Priam's son Troilus in the sanctuary of Apollo Thymbraios. In later, particularly medieval, traditions Troilus is a beautiful young prince toward whom Achilles directs lust; when Troilus refuses he is killed at the altar, and some versions make Achilles's own death retribution for this sacrilege. The First Vatican Mythographer claimed that had Troilus reached adulthood, Troy would have been invincible.

Homer's Iliad is the most famous narrative of Achilles's deeds, and his wrath (mênis Achilléōs) is the poem's central theme, announced in its opening invocation of 'the rage of Peleus' son Achilles.' The epic covers only a few weeks of the decade-long war and does not narrate his death. It begins with Achilles withdrawing from battle after Agamemnon, forced to return the captive Chryseis to end Apollo's plague, seizes Achilles's own war-prize Briseis. Dishonoured and robbed of glory, and urged by his mother Thetis, Achilles refuses to fight and prays that Thetis persuade Zeus to aid the Trojans so his honour may be restored.

When the Trojans under Hector drive the Greeks back to their ships, Patroclus leads the Myrmidons into battle wearing Achilles's armour but is killed by Hector. Stricken with grief, Achilles is consoled by Thetis, who has Hephaestus forge him new armour, including the famous Shield of Achilles. Enraged, Achilles returns to the field, slaughters many Trojans (even battling the river god Scamander), and at last confronts Hector. He chases Hector three times around the walls of Troy before Athena, disguised as Hector's brother Deiphobus, tricks Hector into standing his ground; Achilles kills him and drags his corpse behind his chariot. After holding funeral games for Patroclus, Achilles is moved by Priam, who comes with Hermes's help to plead for his son's body, and grants a truce for Hector's burial — with which the poem ends, Troy's and Achilles's doom still to come.

Later works such as the Aethiopis and Quintus of Smyrna's Posthomerica continue the story. Achilles kills the Amazon queen Penthesilea and grieves over her death, and after the Aethiopian king Memnon, son of Eos, slays Achilles's close companion Antilochus, Achilles takes revenge by killing Memnon in an episode echoing his vengeance for Patroclus.

The exact nature of Achilles's relationship with Patroclus has been disputed since antiquity. In the Iliad it appears as a model of deep, loyal friendship, and Homer does not state that they were lovers, but later authors read it as an erotic bond: in Plato's Symposium the speakers assume they were a couple, while in Xenophon's Symposium Socrates calls their relationship platonic. Commentators across history have interpreted the pair through their own cultural lenses.

The death of Achilles is complex even in the oldest sources. In Iliad Book 22 the dying Hector predicts that Paris and Apollo will slay Achilles at the Scaean Gates (with an arrow to the heel, according to Statius). In Odyssey Book 11 Odysseus meets Achilles's shade in the underworld, where Achilles declares he would rather be a slave to the worst master than king of all the dead, then asks after the exploits of his son Neoptolemus.

Odyssey Book 24 gives the ghost of Agamemnon's account of Achilles's funeral: his bones were mixed with those of Patroclus in his mother's golden vase, those of Antilochus enclosed nearby, funeral games were held, and a great mound was raised on the Hellespont. Another version tells that Achilles fell in love with the Trojan princess Polyxena and sought her hand; Paris, hidden in ambush, shot him with a divine arrow. According to Apollodorus, after death Achilles married Medea in the Elysian Fields.

After Achilles's death his divinely made armour, forged by Hephaestus, became the object of a feud between Odysseus and Ajax the Great. When the contest was decided in Odysseus's favour, Ajax went mad with grief, slaughtered sheep believing them to be his comrades, and, on coming to his senses, killed himself in shame; Odysseus eventually gave the armour to Achilles's son Neoptolemus. Achilles's legendary Pelian Spear, given to him by Chiron, was said to be wieldable by no other man, and a relic claimed to be his spear was preserved for centuries in the temple of Athena at Phaselis in Lycia.

Numerous vase paintings depict a tale not found in literary tradition in which Achilles and Ajax, absorbed in a board game (petteia), are surprised by a Trojan attack and saved only by Athena's intervention.

Achilles's tomb, extant throughout antiquity in the Troad, was venerated by the Thessalians, by Persian and Macedonian commanders including Alexander the Great, and by the Roman emperor Caracalla. His cult was found across the Greek world — on Astypalaea, at Sparta, Elis, and in his homeland Thessaly, as well as in the Magna Graecia cities of Tarentum, Locri, and Croton — amounting to an almost Panhellenic hero cult. Strabo records that near Sigeium stood a temple and monument of Achilles, with monuments also of Patroclus and Antilochus, all honoured by the Ilienses.

The cult was especially remarkable among the Greeks of the northern Black Sea coast. Dedicatory inscriptions from colonies such as Olbia, Berezan, and the Tauric Chersonese attest a heroic cult of Achilles from the sixth century BCE; by the third century CE stelae from Olbia invoke him as Achilles Pontárchēs ('lord of the sea'), protector of the city, venerated alongside Olympian gods. Pliny the Elder mentions an 'island of Achilles' and a peninsula called Dromos Achilleos ('the Race-course of Achilles').

This cult centred on the island of Leuke ('White Island') at the mouth of the Danube, identified with modern Snake Island, where ruins of a square temple were found in 1823 and inscriptions dedicate offerings 'to Achilles, lord of Leuke.' The cult appears to derive from the lost Aethiopis, in which Thetis snatched her son from the funeral pyre and carried him to the mythical Leúkē Nêsos. The Periplus of the Euxine Sea describes how Thetis raised the island for him, how he dwells there with a temple and an archaic statue tended by countless sea birds, and how Achilles appears to sailors in dreams to instruct them where to anchor.

Several Greek port cities bore his name, including an Achílleion built by Mytilenean settlers near his presumed burial mound in the Troad. The kings of Epirus claimed descent from Achilles through Neoptolemus, and Alexander the Great, son of the Epirote princess Olympias, therefore claimed this descent and strove to emulate his ancestor, visiting the tomb at Achilleion when passing Troy; the emperor Caracalla likewise held games around the tumulus in 216 CE.

Aeschylus wrote a trilogy about Achilles, known to modern scholars as the Achilleis, covering his deeds, his slaying of Hector, and his death; its first part, The Myrmidons, dramatized the Achaean army's attempts to end his quarrel with Agamemnon. In Plato's Symposium, Phaedrus notes that Aeschylus made Achilles the lover and Patroclus the beloved, and argues this is mistaken since Achilles was the younger and more beautiful. Sophocles also wrote The Lovers of Achilles, surviving only in fragments, and toward the end of the fifth century BCE a more negative view of Achilles appears in Euripides's Hecuba, Electra, and Iphigenia in Aulis.

In philosophy, Zeno of Elea built one of his paradoxes on a footrace between 'swift-footed' Achilles and a tortoise, arguing that Achilles could never overtake a tortoise given a head start, in order to show motion and change to be illusions. In the Platonic dialogue Hippias Minor, Socrates and the sophist Hippias debate honesty using Achilles and Odysseus as examples, disputing whether someone who does wrong on purpose is better than one who does wrong unintentionally.

The Romans, tracing their lineage to Troy, took a largely negative view of Achilles: Virgil calls him a savage and merciless man-butcher, and Horace depicts him slaying women and children, while Catullus, Propertius, and Ovid emphasize his erotic career. This disparaging tradition continued in the Latin accounts of Dictys Cretensis and Dares Phrygius and in medieval works such as Benoît de Sainte-Maure's Roman de Troie and Guido delle Colonne's Historia destructionis Troiae, the most widely read versions of the Matter of Troy until the seventeenth century.

Achilles has been a recurring figure in modern literature. He appears in Dante's Inferno among the lustful, and in Shakespeare's Troilus and Cressida as a hero gone idle who has his Myrmidons murder an unarmed Hector. Later treatments include Goethe's poem fragment Achilleis (1799), Stanisław Wyspiański's drama Achilles (1899), Christa Wolf's Kassandra (1983), and a wave of recent novels — among them David Malouf's Ransom (2009), Madeline Miller's The Song of Achilles (2011), winner of the 2012 Orange Prize for Fiction, and Pat Barker's The Silence of the Girls (2018).

In the visual arts, the subject of Achilles among the daughters of Lycomedes was treated by Anthony van Dyck and Nicolas Poussin, among others. Peter Paul Rubens produced an entire series on Achilles's life, including Thetis dipping the infant Achilles into the river Styx, Achilles educated by the centaur Chiron, the wrath of Achilles, the death of Hector, Thetis receiving the arms of Achilles from Vulcanus, and the death of Achilles.