Thāj (Arabic: ثَاج) is an archaeological site and ancient town located west of Jubail in the Eastern Province, Saudi Arabia. It is associated with the Hellenistic era. Many artifacts including pottery and jewellery have been discovered at Thāj, some of which are currently held in the British Museum.

The archaeological site of Thāj can be found around 90 kilometres west of Jubail at the border of a small village known as Sabkha, all within the Eastern Province of Saudi Arabia.

The city of Thāj generally dates back to the 3rd century BCE, during the Hellenistic period. The city was also an important urban centre in at least the 1st millennium BCE. During the 7th century CE, some of the remaining inhabitants accepted the call of Islam which was slowly spreading at the time.

Carvings, wall reliefs, and pottery were discovered at Thāj in the 1960s and then stored in the British Museum. Then in 1968, a Danish exploration team visited the site. Later in the 1980s, excavations revealed the city of Thāj and the stone wall which surrounded it. In 2009, more excavations were conducted which revealed the grave of a young girl along with several burial goods, including a golden funerary mask.

• Ancient towns in Saudi Arabia
• Cities of the ancient Near East