Najd (Arabic: نَجْدٌ, pronounced [nad͡ʒd]), or the Nejd, forms the geographic center of Saudi Arabia accounting for about a third of the country's modern population and, since the Emirate of Diriyah, acting as the base for all unification campaigns by the House of Saud to bring Arabia under a single polity and Islamic jurisprudence.

Landscape of the Shammar Mountains range
CountrySaudi Arabia
Saudi regionsRiyadh, Al-Qassim, Ha'il

Historic Najd was divided into three modern administrative regions still in use today. The Riyadh region, featuring Wadi Hanifa and the Tuwaiq escarpment, which houses easterly Yamama with the Saudi capital, Riyadh since 1824, and the Sudairi region which has its capital in Majmaah. The second administrative unit, Al-Qassim, houses the fertile oases and date palm orchards spread out in the region's highlands along Wadi Rummah in central Najd with its capital in Buraidah (second largest Najdi city) with the region historically contested by the House of Rashid to its north and the House of Saud to its east and south. The third administrative unit is northerly Ḥaʼil, which features the mountains of Jabal Shammar housing the Tayy capital of Ḥaʼil.