Coordinates: 25°25′46″N 49°37′19″E / 25.42944°N 49.62194°E / 25.42944; 49.62194

Al-Ahsa, sometimes Al-Hasa, El Hasa, or Hadjar (Arabic: الأحساء‎ al-Aḥsāʾ, locally al-Ḥasāʾ; Turkish: Lahsa) is a traditional oasis region in eastern Saudi Arabia whose name is used by the Al-Ahsa Governorate, which makes up much of that country's Eastern Province. The oasis is located about 60 km inland from the Persian Gulf.

Al-Ahsa is part of the region known historically as Al-Bahrayn, which includes the eastern coast of the Arabian Peninsula down to the borders of Oman, and also includes the island of Awal (modern-day Bahrain).

Al-Hasa contains one of the largest concentrations of Shia Muslims in predominantly Sunni Saudi Arabia.

In Al-Ahsa city there are:

Al-Ahsa has been inhabited since prehistoric times, due to its abundance of water in an otherwise arid region.^{[citation needed]} Natural fresh-water springs have surfaced at oases in the region for millennia, encouraging human habitation and agricultural efforts (date palm cultivation especially) since prehistoric times. Recently, Al-Ahsa Oasis has nominated as one of the seven wonders of the world.