Qais

Qays ʿAylān (Arabic: قيس عيلان‎‎), often referred to simply as Qays (also spelled Qais, Kais or Kays) were an Arab tribal grouping branched from the Mudhar section of the Adnanites. The tribe does not appear to have functioned as a unit in the pre-Islamic era. However, by the early Umayyad, its constituent tribes consolidated into one of the main tribo-political factions of the caliphate.

The major constituent tribes or tribal groupings of the Qays were the Hawazin, Banu 'Amir, Banu Thaqif, Banu Sulaym, Banu Ghani, Bahila and Banu Muharib. Many of these tribes or their clans migrated from the Arabian Peninsula and established themselves in northern Syria and Upper Mesopotamia, which long became their abode. From there they governed on behalf of the caliphs or rebelled against them. The power of Qays as a unified group diminished with the rise of the Abbasid Caliphate which did not derive its military strength solely from the Arab tribes. Nonetheless, individual Qaysi tribes remained a potent force and some migrated to North Africa and Iberia where they carved out their own power.

The full name of the tribal confederation is Qays ʿAylān or Qays ibn ʿAylān, though it is most frequently referred to simply as Qays; occasionally in Arabic poetry, it is referred to solely as ʿAylān. Members of the Qays are referred to as al-Qaysĭyūn (sing. Qaysī), transliterated in English-language sources as "Qaysites" or "Kaisites". As an ethno-political group, the Qays are referred to in contemporary sources as al-Qaysīyya. Unlike most Arab tribes, the sources seldom use the term Banū (sons of) when referring to the descendants of Qays.

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