Shamash was the ancient Mesopotamian sun god, also known as Utu. He was believed to see everything that happened in the world every day, and was therefore responsible for justice and protection of travelers. As a divine judge, he could be associated with the underworld. Additionally, he could serve as the god of divination, typically alongside the weather god Adad. While he was universally regarded as one of the primary gods, he was particularly venerated in Sippar and Larsa.The moon god Nanna (Sin) and his wife Ningal were regarded as his parents, while his twin sister was Inanna (Ishtar). Occasionally other goddesses, such as Manzat and Pinikir, could be regarded as his sisters too. The dawn goddess Aya (Sherida) was his wife, and multiple texts describe their daily reunions taking place on a mountain where the sun was believed to set. Among their children were Kittum, the personification of truth, dream deities such as Mamu, as well as the god Ishum. Utu's name could be used to write the names of many foreign solar deities logographically. The connection between him and the Hurrian solar god Shimige is particularly well attested, and the latter could be associated with Aya as well.

Larsa, also referred to as Larancha/Laranchon by Berossos and connected with the biblical Ellasar, was an important city-state of ancient Sumer, the center of the cult of the sun god Utu with his temple E-babbar. It lies some 25 km (16 mi) southeast of Uruk in Iraq's Dhi Qar Governorate, near the east bank of the Shatt-en-Nil canal at the site of the modern settlement Tell as-Senkereh or Sankarah.