White slavery refers to the enslavement of any of the world's European ethnic groups throughout human history, whether perpetrated by non-Europeans or by other Europeans. Slavery in ancient Rome was frequently dependent on a person's socio-economic status and national affiliation, and thus included European slaves. It was also common for European people to be enslaved and traded in the Muslim world; European women, in particular, were highly sought-after to be concubines in the harems of many Muslim rulers. Examples of such slavery conducted in Islamic empires include the Arab slave trade, the Barbary slave trade, and the Black Sea slave trade, among others. It was common for Europeans to be traded alongside Africans, Turks, Iranians, and sometimes other Arabs.