Norse
Njörðr
sea, wind, wealth
Roman tradition. See the whole pantheon.

Roman god of water and horses; his early festival, the Neptunalia, was in high summer.
Greek counterpart: Poseidon on thegreekgods.org. Roman and Greek versions share names and stories in many places but began as different cults.
Deities in other traditions who share a theme with Neptune: sea and waters. This is overlap in one area only.
Norse
sea, wind, wealth
Norse
the sea, brewer of the gods' ale
Norse
drowning, the sea's net
Egyptian
the primeval waters
Egyptian
Nile, fertility, kingship
Mesopotamian
the primeval sea, mother of the gods
Mesopotamian
fresh water below the earth
Mesopotamian
salt water, primordial mother