Neptune

Neptune is the Roman god of the sea, while Poseidon is his earlier Greek counterpart from whom Neptune was largely adapted. The key difference is that Neptune was originally an Italic deity associated primarily with freshwater springs before he absorbed Poseidon's oceanic domain as Greek influence spread through Rome. Poseidon, by contrast, was always associated with the sea, earthquakes, and horses from the earliest Greek traditions, while Neptune's freshwater origins remained part of his identity.

The Neptunalia was Neptune's primary festival, celebrated annually on July 23 in the Roman calendar. During this midsummer festival, Romans built temporary huts or shelters (umbrae) from tree branches, where they feasted and sought relief from the summer heat. The festival emphasized Neptune's connection to freshwater and springs, reflecting his original Italic identity before his full assimilation to Poseidon's maritime domain.

Neptune's primary consort was Salacia, a Roman goddess of salt water and the sea whose name derives from the Latin word for salt (sal). In Roman tradition, Salacia was said to have hidden from Neptune in the Atlantic Ocean before being persuaded to marry him, which some scholars interpret as an allegory for the sea's depths. Neptune also had a relationship with Amphitrite, borrowed from Greek mythology where she was Poseidon's wife.

Neptune was originally an Italic deity associated with freshwater springs and inland waters, not the open sea. His early worship in Rome focused on agricultural irrigation and freshwater supply rather than maritime matters. His identification with the Greek Poseidon and his full assumption of oceanic power occurred gradually as Rome expanded and absorbed Greek religious traditions, particularly after Rome became a major naval power during the Punic Wars in the 3rd century BC.