Poseidon in the context of "Thessalus"

Classical mythology, also known as Greco-Roman mythology or Greek and Roman mythology, is the collective body and study of myths from the ancient Greeks and ancient Romans. Mythology, along with philosophy and political thought, is one of the major survivals of classical antiquity throughout later, including modern, Western culture. The Greek word mythos refers to the spoken word or speech, but it also denotes a tale, story or narrative.

As late as the Roman conquest of Greece during the last two centuries Before the Common Era and for centuries afterwards, the Romans, who already had gods of their own, adopted many mythic narratives directly from the Greeks while preserving their own Roman (Latin) names for the gods. As a result, the actions of many Roman and Greek deities became equivalent in storytelling and literature in modern Western culture. For example, the Roman sky god Jupiter or Jove became equated with his Greek counterpart Zeus; the Roman fertility goddess Venus with the Greek goddess Aphrodite; and the Roman sea god Neptune with the Greek god Poseidon.

Religious practices in ancient Greece encompassed a collection of beliefs, rituals, and mythology, in the form of both popular public religion and cult practices. The application of the modern concept of "religion" to ancient cultures has been questioned as anachronistic. The ancient Greeks did not have a word for 'religion' in the modern sense. Likewise, no Greek writer is known to have classified either the gods or the cult practices into separate 'religions'. Instead, for example, Herodotus speaks of the Hellenes as having "common shrines of the gods and sacrifices, and the same kinds of customs".

Most ancient Greeks recognized the twelve major Olympian gods and goddesses—Zeus, Hera, Poseidon, Demeter, Athena, Ares, Aphrodite, Apollo, Artemis, Hephaestus, Hermes, and either Hestia or Dionysus—although philosophies such as Stoicism and some forms of Platonism used language that seems to assume a single transcendent deity. The worship of these deities, and several others, was found across the Greek world, though they often have different epithets that distinguished aspects of the deity, and often reflect the absorption of other local deities into the pan-Hellenic scheme.

Posidonius (/ˌpɒsɪˈdoʊniəs/; Ancient Greek: Ποσειδώνιος Poseidṓnios, "of Poseidon") "of Apameia" (ὁ Ἀπαμεύς) or "of Rhodes" (ὁ Ῥόδιος) (c. 135 – c. 51 BC), was a Greek politician, astronomer, astrologer, geographer, historian, mathematician, and teacher native to Apamea, Syria. He was considered the most learned man of his time and, possibly, of the entire Stoic school. After a period learning Stoic philosophy from Panaetius in Athens, he spent many years in travel and scientific researches in Spain, Africa, Italy, Gaul, Liguria, Sicily and on the eastern shores of the Adriatic. He settled as a teacher at Rhodes where his fame attracted numerous scholars. Next to Panaetius he did most, by writings and personal lectures, to spread Stoicism to the Roman world, and he became well known to many leading men, including Pompey and Cicero.

His works are now lost, but they proved a mine of information to later writers. The titles and subjects of more than twenty of them are known. In common with other Stoics of the middle period, he displayed syncretic tendencies, following not just the earlier Stoics, but making use of the works of Plato and Aristotle. A polymath as well as a philosopher, he took genuine interest in natural science, geography, natural history, mathematics and astronomy. He sought to determine the distance and magnitude of the Sun, to calculate the diameter of the Earth and the influence of the Moon on the tides.

In Greek mythology, the Nereids or Nereides (/ˈnɪəriɪdz/ NEER-ee-idz; Ancient Greek: Νηρηΐδες, romanized: Nērēḯdes; sg. Νηρηΐς, Nērēḯs, also Νημερτές) are sea nymphs (female spirits of sea waters), the 50 daughters of the 'Old Man of the Sea' Nereus and the Oceanid Doris, sisters to their brother Nerites. They often accompany Poseidon, the god of the sea, and can be friendly and helpful to sailors (such as the Argonauts in their search for the Golden Fleece).

Neptune (Latin: Neptūnus [nɛpˈtuːnʊs]) is the god of freshwater and the sea in the Roman religion. He is the counterpart of the Greek god Poseidon. In the Greek-inspired tradition, he is a brother of Jupiter and Pluto, with whom he presides over the realms of heaven, the earthly world (including the underworld), and the seas. Salacia is his wife.

Depictions of Neptune in Roman mosaics, especially those in North Africa, were influenced by Hellenistic conventions. He was likely associated with freshwater springs before the sea; his festival, Neptunalia, took place on July 23, during the peak of summer when water was scarcest. Like Poseidon, he was also worshipped by the Romans as a god of horses, Neptunus equestris, who was also a patron of horse-racing.

In ancient Greek religion and mythology, the twelve Olympians are the major deities of the Greek pantheon, commonly considered to be Zeus, Poseidon, Hera, Demeter, Aphrodite, Athena, Artemis, Apollo, Ares, Hephaestus, Hermes, and either Hestia or Dionysus. They were called Olympians because, according to tradition, they resided on Mount Olympus.

Besides the twelve Olympians, there were many other cultic groupings of twelve gods.

In ancient Greek religion and mythology, Demeter (/dɪˈmiːtər/; Attic: Δημήτηρ Dēmḗtēr [dɛːmɛ́ːtɛːr]; Doric: Δαμάτηρ Dāmā́tēr) is the Olympian goddess of the harvest and agriculture, presiding over crops, grains, food, and the fertility of the earth. Although Demeter is mostly known as a grain goddess, she also appeared as a goddess of health, birth, and marriage, and had connections to the Underworld. She is also called Deo (Δηώ Dēṓ).

In Greek tradition, Demeter is the second child of the Titans Rhea and Cronus, and sister to Hestia, Hera, Hades, Poseidon, and Zeus. Like her other siblings except Zeus, she was swallowed by her father as an infant and rescued by Zeus. Through Zeus, she became the mother of Persephone, a fertility goddess and resurrection deity. One of the most notable Homeric Hymns, the Homeric Hymn to Demeter, tells the story of Persephone's abduction by Hades and Demeter's search for her. When Hades, the King of the Underworld, wished to make Persephone his wife, he abducted her from a field while she was picking flowers, with Zeus's leave. Demeter searched everywhere to find her missing daughter to no avail until she was informed that Hades had taken her to the Underworld. In response, Demeter neglected her duties as goddess of agriculture, plunging the earth into a deadly famine where nothing would grow, causing mortals to die. Zeus ordered Hades to return Persephone to her mother to avert the disaster. However, because Persephone had eaten food from the Underworld, she could not stay with Demeter forever, but had to divide the year between her mother and her husband, explaining the seasonal cycle as Demeter does not let plants grow while Persephone is gone.

The religious beliefs and practices of Mycenaean Greece (c. 1600–1100 BC) are difficult to discern due to limited archeological, iconographical, and material records. Existing evidence suggests that the Mycenaean religion was the mother of the Greek religion, sharing many divinities later found in classical Greece (510–323 BC), including Zeus, Poseidon, and Dionysus. Several Mycenaean religious customs, such as animal sacrifices and votive offerings, survived into the Greek period, as did terms and concepts such as theos (deity), hieros (holy man), nawos (temple), and temenos (land cut off and assigned for communal purposes).

John Chadwick noted that at least six centuries lie between the earliest presence of Proto-Greek speakers in Hellas and the earliest inscriptions in the Mycenaean script known as Linear B, during which concepts and practices will have fused with indigenous pre-Greek beliefs, and—if cultural influences in material culture reflect influences in religious beliefs—with Minoan religion. As for these texts, the few lists of offerings that give names of gods as recipients of goods reveal little about religious practices, and there is no other surviving literature.

Hades (/ˈheɪdiːz/; Ancient Greek: ᾍδης, romanized: Hā́idēs, Attic Greek: [háːi̯dεːs], later [háːdeːs]), in the ancient Greek religion and mythology, is the god of the dead and riches and the King of the underworld, with which his name became synonymous. Hades was the eldest son of Cronus and Rhea, although this also made him the last son to be regurgitated by his father. He and his brothers, Zeus and Poseidon, defeated, overthrew, and replaced their father's generation of gods, the Titans, and claimed joint sovereignty over the cosmos. Hades received the underworld, Zeus the sky, and Poseidon the sea, with the solid earth, which was long the domain of Gaia, available to all three concurrently. In artistic depictions, Hades is typically portrayed holding a bidentand wearing his helm with Cerberus, the three-headed guard-dog of the underworld, standing at his side.

Roman-era mythographers eventually equated the Etruscan god Aita,and the Roman gods Dis Pater and Orcus, with Hades, and merged all these figures into Pluto, a Latinisation of Plouton (Ancient Greek: Πλούτων, romanized: Ploútōn), itself a euphemistic title (meaning "the rich one") often given to Hades.