population of Yemen is 18,078,035 (2001 estimate). The average population density is 34 persons per sq km (89 per sq mi). Although more than one and a half times its size in land area, the former South Yemen had less than one-third the population of the former North Yemen in the late 1980s. The population of southern Yemen is concentrated in a few areas, including Al Mukalla and the other towns of Hadhramaut, the highlands north and east of Aden, and above all, in Aden proper and its metropolitan area.

The people of Yemen are overwhelmingly Arabic-speaking Muslims of Mediterranean stock. Yemenis of “northern” origin are thought to have descended from Mesopotamians who entered the region in the 1st millennium BC. The “southern” group represents the South Arabian stock, and the Arabic of the rural areas of former South Yemen is still heavily determined by the ancient South Arabian languages. The two groups maintain disparate genealogies and historical traditions concerning their roles and origins: The northern Yemenis trace their ancestry to (Ishmael) through his descendant 'Adnan, whereas their southern nationmen claim descent from Qahtan

Unlike other people of the Arabian Peninsula who have historically been nomads or semi-nomads, Yemenis are almost entirely sedentary and live in small villages and towns scattered throughout the highlands and coastal regions. Yemenis are separated into two principal Islamic religious groups: the Zaidi sect of the Shi'a, found in the north and northwest, and the Shafa'i school of Sunni Muslims, found in the south and southeast. Yemenis are mainly of Semitic origin, although African strains are present among inhabitants of the coastal region. Arabic is the official language, although English is increasingly understood in major cities. In the Mahra area (the extreme east), several non-Arabic languages are spoken. When the former states of north and south Yemen were accomplished, most resident minority groups departed.