Zaydism (Arabic: الزَّيْدِيَّة, romanized: az-Zaydiyya) is a branch of Shia Islam that emerged in the eighth century following Zayd ibn Ali's unsuccessful rebellion against the Umayyad Caliphate.

[4] Zaydis regard rationalism as more important than Quranic literalism and historically were quite tolerant towards Sunni Shafi'ism, a religion of about half of the Yemenis.

[6] The Zaydis in Yemen had initially lived in the highlands and the northern territories, but extent of their dominance away from their capital of 7 centuries, Saada, had been changing over time.

Some sources argue that Zaydism is simply a philosophy of political government that justifies the overthrow of unjust rulers and prioritizes those who are Ahl al-Bayt.

[13][14] Haider[15] states that mainstream Zaydism (Hadawi) is a result of interaction of two currents, Batrism and Jarudism, their followers brought together during the original Zayd's rebellion.

[15][17] The following table summarizes the differences between Batri and Jarudi beliefs per Haider:[18] Zaydis' theological literature puts an emphasis on social justice and human responsibility, and its political implications, i.e. Muslims have an ethical and legal obligation by their religion to rise up and depose unjust leaders including unrighteous sultans and caliphs.

Muhammad al-Baqir did not engage in political action and the followers of Zayd believed that a true Imām must fight against corrupt rulers.

[20] The renowned Muslim jurist Abu Hanifa, who is credited with founding the Hanafi school of Sunni Islam, delivered a fatwā or legal statement in favour of Zayd in his rebellion against the Umayyad ruler.

They therefore consider the companions wrong in failing to recognise 'Ali as the legitimate Caliph and deny legitimacy to Abu Bakr, Umar and Uthman; however, they avoid accusing them.

Its views, although predominant among the later Zaydis, especially in Yemen under the Hadawi sub-sect, became extinct in Iraq and Iran due to forced conversion of the present religious sects to Twelver Shi'ism by the Safavid dynasty.

[citation needed] The third group is known as the Batriyya, Tabiriyya, or Salihiyya for Kathir an-Nawa al-Abtar and Hasan ibn Salih.

[28] Zayd bitterly scolds the "rejectors" (rafidha) who deserted him, an appellation used by Salafis to refer to Twelver Shi'a to this day.

".Jafar al-Sadiq's love for Zayd ibn Ali was so immense that he broke down and cried upon reading the letter informing him of his death and proclaimed: From God we are and to Him is our return.

I swear by God that my uncle is a martyr just like the martyrs who fought along with God’s Prophet or Ali or Al-Hassan or Al-HusseinHowever, in other hadiths, narrated in Al-Kafi, the main Shia book of hadith, Zayd ibn Ali is criticized by his half-brother, Imam Muhammad al-Baqir, for his revolt against the Umayyad Dynasty.

The Alavids established a Zaydi state in Deylaman and Tabaristan (northern Iran) in 864;[47] it lasted until the death of its leader at the hand of the Sunni Samanids in 928.

Al-Hadi ila'l-Haqq Yahya, a descendant of Imam Hasan ibn Ali, founded this Rassid state at Sa'da, al-Yaman, in c. 893–897.

In the 21st century, the most prominent Zaidi movement is the Shabab Al Mu'mineen, commonly known as Houthis, who have been engaged in an uprising against the Yemeni Government, causing a grave humanitarian crisis in north Yemen.

[56] On 21 September 2014, an agreement was signed in Sana'a under UN patronage essentially giving the Houthis control of the government after a decade of conflict.

[57] Tribal militias then moved swiftly to consolidate their position in the capital, with the group officially declaring direct control over the state on 6 February 2015.

[58] This outcome followed the removal of Yemen's President Ali Abdullah Saleh in 2012 in the wake of protracted Arab Spring protests.