He is the strongest of the Titans. He possesses the most stamina and highest degree of durability of the Titans or Olympian gods with the possible exception of Hercules.
Atlas is a son of Iapetus the Titan and Clymene the Oceanid. A more obscure version names his mother "Asia", another Oceanid. In either case, his paternal grandparents were Uranus and Gaea. His maternal grandparents were Oceanus and Tethys, both Titans and siblings of Iapetus. His brothers were Epimetheus, Menoetius and Prometheus. (A fifth brother called "Hesperus" is mentioned in a single ancient source).
There is another figure called Atlas in Greek legend, the first King of Atlantis. The other Atlas is named son of Poseidon and Cleito. His paternal grandparents were Cronus and Rhea, both Titans. His maternal grandparents were Evenor and Leucippe. Unclear if the two Atlases are versions of the same figure or simply figures who share a name. Cleito and Evenor have both been depicted as deities in "Man-Thing" stories but not Olympians.
Atlas took part in the Titanomachy, a battle between the Titans and the Olympians. He was defeated and sentenced by Zeus to the eternal punishment of forever bearing on his shoulders the pillars that keep earth and heaven apart. The location of his punishment were the so-called Atlas mountains, a historical mountain range of Northern Africa. Today they are held by Morocco, Algeria and Tunisia. Atlas holds the weight or the heavens keeping the the sky and the earth separate at the "Axis Mundi." The Axis Mundi is located wherever the seat of earthly power is currenty located. Presently, it's location is in Washington, D.C.
He figures in a couple of contradictory tales of mortal heroes. He is said to have been visited by Perseus but denied the mortal his hospitality. Perseus then used the decapitated head of Medusa to petrify the old Titan, leaving a mountain behind. Yet a very-much-alive Atlas is said to have encountered Hercules, a great-grandson of Perseus. The younger hero asked Atlas for help in gaining the golden apples guarded by some of Atlas' daughters. Hercules briefly took over the burden of holding the pillars on his shoulders. Atlas did return with the apples but was tempted to stay free and travel around. Hercules begged him to hold the pillars again for a moment, just to get a pad for his head. Atlas agreed and was tricked in resuming his old burden. Hercules escaped with the apples.
Atlas figures prominently in the ancestry of a number of deities and mortal heroes:
*His mating with Pleione the Oceanid resulted in the birth of the Pleiades, seven daughters identified with prominent stars. By name they were:
**Alcyone. She mated with Poseidon and was mother of four children. Sons Anthas, Hyperenor and Hyrieus were founders of various cities. The latter was father to Orion the giant. Aethusa , Alcyone's daughter, was a lover of Apollo and mother to Eleutheros, a famed singer.
**Celaeno. She mated with Poseidon. Her sons were Euphemos, Lucus ("Wolf") and Nycteus. The latter is known as father of Callisto.
**Electra. She mated with Zeus. Her sons were Dardanus, Emathion and Iasion. Dardanus is known as the founder of Troy and its Royal House. Emathion as a King of Samothrace, connected to the local religious mysteries. Iasion was a lover of Demeter. Electra is mentioned as mother of Harmonia (Harmony) in some versions. However in the best known version Harmonia is a daughter of the deities Ares and Aphrodite.
**Maia. She mated with Zeus. Her son was the god Hermes/Mercury.
**Merope. She married the mortal Sisyphus, King of Corinth. Their sons were Almus, Glaucus and Thersander. Almus is mentioned as a minor ruler in Boeotia. Glaucus was the father of famous hero Bellerophon, master of Pegasus. Thersander's children were all adopted by Athamas. His lineage figures in tales of Thessaly.
**Sterope. She mated with the god Ares and the mortal Oenomaus, King of Pisa. Her sons were Dysponteus and Leucippus. The former was founder of a city. The latter is known for a love story with Daphne. Far better known is Sterope's daughter, Hippodamia. She married Pelops and was the matriarch of the Pelopid dynasty. Her descendants include rulers of Mycenae (starting with Atreus), Sparta (starting with Menelaus) and Athens (starting with Theseus).
**Taygete. Mated with Zeus. Her son Lacedaemon married a woman named Sparta. He founded a city named after his wife and a country named after himself. He is the ancestor of the Lacedaemonians/Spartans.
*His mating with Hesperis, a daughter of Zeus and Themis, resulted in the birth of the Hesperides. They were six daughters: Aegle, Arethusa, Erytheis, Erythia, Hesperethusa, Hesperia. They were taked by Hera in guarding the golden apples, gifths granted to her by Gaea.
**Aegle mated with Helius (the Sun), a second-generation Titan. They were the parents of the Charites/Graces (Aglaia, Auxo, Charis, Cleta, Euphrosyne, Hegemone, Pasithea, Phaenna and Thalia).
However the same daughters are elsewhere attributed to Zeus and Eurynome the Oceanid. Pasithea is the most notable daughter because of her further connections. She married the god Hypnos (Sleep) and was mother of Morpheus (God of Dreams), Phobetor (God of Nightmares) and Phantasos (apparition, only took the form of inanimate objects).
*His mating with Aethra resulted in the birth of a single son and ten daughters. Hyas, the son, was killed by the lion. His sisters (Ambrosia, Cleeia, Coronis, Eudore, Pedile, Phaeo, Phaesyla, Phyo, Polyxo and Thyone) mourned deeply until turned into stars. Ambrosia and Polyxo are known as members of Dyonusus' entourage and fierce fighters.
*His daughter Calypso is featured prominently in the Odyssey as an immortal lover of Odysseus. Later mythographers often confused her with Circe, attributing the same tales to either goddess. Latinus, Nausinous, Nausithous and Telegonus are described as sons of Odysseus by either Calypso or Circe. Telegonus was the protagonist of a lost epic, a search for his missing father. He killed Odysseus in a chance encounter with him.
*His daughter Maera married Tegeates. They were the founders of the city Tegea in Arcadia. A number of their descendants supposedly migrated to Crete.