Hejaz is a historical region of the Arabian Peninsula that includes the majority of the western region of Saudi Arabia, covering the cities of Mecca, Medina, Jeddah, Tabuk, Yanbu, Taif and Al-Bahah. It is thus known as the "Western Province", and it is bordered in the west by the Red Sea, in the north by Jordan and the Gulf of Suez, in the east by the Najd, and in the south by Yemen. Its largest city is Jeddah, which is the second-largest city in Saudi Arabia, with Mecca and Medina, respectively, being the third- and fourth-largest cities in the country.

As the location of the holy cities of Mecca and Medina, respectively the first and second holiest sites in Islam, the Hejaz is significant in the Arabo-Islamic historical and political landscape. This region is the most populated in Saudi Arabia, and Arabic is the predominant language, as in the rest of Saudi Arabia, with Hejazi Arabic being the most widely spoken dialect here. Some Hejazis are of ethnically diverse origins, although the vast majority are of Arab origin.

According to Islamic tradition, this region is the birthplace of the Islamic prophet Muhammad, who was born in Mecca, which is held to be founded by his believed ancestors Abraham, Ishmael, and Hagar. The area became part of his empire through the early Muslim conquests, and it formed part of successive caliphates, first the Rashidun Caliphate, followed by the Umayyad Caliphate, and finally the Abbasid Caliphate. The Ottoman Empire held partial control over the area; after its dissolution, an independent Kingdom of Hejaz existed briefly in 1925 before being conquered by the neighbouring Sultanate of Nejd, creating the Kingdom of Hejaz and Nejd. In September 1932, the Kingdom of Hejaz and Nejd joined the Saudi dominions of Al-Hasa and Qatif, creating the unified Kingdom of Saudi Arabia.

The name of the region is derived from a verb ḥajaza (حَجَز), from the Arabic root ḥ-j-z (ح-ج-ز), meaning "to separate", and it is so called as it separates the land of the Najd in the east from the land of Tihāmah in the west.

One or possibly two megalithic dolmen have been found in Hejaz.

The Hejaz includes both the Mahd adh-Dhahab ("Cradle of the Gold") (23°30′13″N 40°51′35″E / 23.50361°N 40.85972°E / 23.50361; 40.85972) and a water source, now dried out, that used to flow 600 miles (970 km) north east to the Persian Gulf via the Wādi Al-Rummah and Wādi Al-Bātin system. Archaeological research led by of Boston University and the University of Qassim indicates that the river system was active in 2500–3000 BCE.

According to Al-Masudi the northern part of Hejaz was a dependency of ancient Israel, and according to Butrus al-Bustani the Jews in Hejaz established a sovereign state. The German orientalist Ferdinand Wüstenfeld believed that the Jews established a state in northern Hejaz.

According to Arab and Islamic sources, the civilization of Mecca started after Ibrāhīm (Abraham) brought his son Ismāʿīl (Ishmael) and wife Hājar (Hagar) here, for the latter two to stay. The Adnanites were a tribal confederation of the Ishmaelite Arabs, who trace their lineage back to Ishmael son of the Islamic prophet and patriarch Abraham and his wife Hagar through Adnan, who originate from the Hejaz. Some people from the Yemeni tribe of Jurhum settled with them, and Isma'il reportedly married two women, one after divorcing another, at least one of them from this tribe, and helped his father to construct or re-construct the Ka'bah, which would have social, religious, political and historical implications for the site and region.