The Hashemite Kingdom of Hejaz (Arabic: المملكة الحجازية الهاشمية, Al-Mamlakah al-Ḥijāziyyah Al-Hāshimiyyah) was a state in the Hejaz region in the Middle East (modern-day western Saudi Arabia), the western portion of the Arabian peninsula ruled by the Hashemite dynasty. It achieved national independence in June 1916 after the destruction of the Ottoman Empire by the British Empire during the First World War when the Sharif of Mecca fought in alliance with the British Imperial forces to drive the Ottoman Army from the Arabian Peninsula during the Arab Revolt.
The United Kingdom promised King Ali of Hejaz a single independent Arab state that would include modern day Syria, Iraq, Palestine and Jordan in addition to the Hejaz region. However, at the end of the First World War, the Treaty of Versailles turned Syria into a French protectorate while Iraq, Palestine and Transjordan became British protectorates. The relations with the British Empire further deteriorated when Zionist Jews were allowed to return to Palestine. The newly independent kingdom had a brief life and then was conquered in 1925 by the neighbouring Sultanate of Nejd under a resurgent House of Saud, creating the Kingdom of Hejaz and Nejd.
On 23 September 1932, the Kingdom of Hejaz and Nejd joined the Saudi dominions of al-Hasa and Qatif, as the unified Kingdom of Saudi Arabia.