Al-Ahsa Oasis

Al-Ahsa Oasis (Arabic: الْأَحْسَاء, al-ʾAhsā), also known as al-Ḥasāʾ (الْحَسَا) or Hajar (هَجَر), is an oasis and historical region in eastern Saudi Arabia. Al-Ahsa Governorate, which makes up much of the country's Eastern Province, is named after it. The oasis is located about 60 km (37 miles) inland from the coast of the Persian Gulf. Al-Ahsa Oasis comprises four main cities and 22 villages. The cities include Al-Mubarraz and Al-Hofuf, two of the largest cities in Saudi Arabia.

With an area of nearly 85.4 km2 (33.0 sq mi), Al-Ahsa Oasis is the largest oasis in the world. The majority of the oasis is located in the Empty Quarter, also referred to as, Rub' al Khali in Arabic. This covers almost three-quarters of the land in the oasis, while residential areas constitute 18%. There are more than 2.5 million palm trees including date palms in the oasis, which is fed from a huge underground aquifer and irrigated by the flow of more than 280 artesian springs, allowing year-round agriculture in a region that is otherwise sand desert. The oasis became a World Heritage site in 2018. It has also been part of the UNESCO Creative Cities Network since December 2015. According to one author, the oases of Al-Ahsa and Al Ain (in the U.A.E., on the border with Oman) are the most important in the Persian Gulf region.