Ijtihad (Arabic: اجتهاد‎, ʼijtihād) is the making of a decision in Islamic law (sharia) by personal effort (jihad), independently of any school (madhhab) of jurisprudence (fiqh). as opposed to taqlid, copying or obeying without question.

Ijtihad is mainly associated with the Usuli Shi'a Muslim Jafari school of jurisprudence. To be valid and accepted it has to be rooted in the Qur'an and the hadith and it is required that no established doctrine rules the case. A mujtahid is an Islamic scholar who is competent to interpret sharia by ijtihad. Whereas Akhbari Shi'a Muslim outright reject ijtihad and do not imitate a mujtahid who practice ijtihad.

The word derives from the three-letter Arabic verbal root of ج-ه-د J-H-D (jahada, "struggle"): the "t" is inserted because the word is a derived stem VIII verb. In Islamic political theory, ijtihad is often counted as one of the essential qualifications of the caliph, e.g. by Al-Baghdadi (1037) or Al-Mawardi (1058). Al-Ghazali dispenses with this qualification in his legal theory and delegates the exercise of ijtihad to the scholars of religion (ulema).

Hamza Yusuf Hanson is an American Islamic scholar, and (with Zaid Shakir and Hatem Bazian) is co-founder of Zaytuna College in Berkeley, California, United States. He is a convert to Islam, and is one of the signatories of A Common Word Between Us and You, an open letter by Islamic scholars to Christian leaders, calling for peace and understanding. He has described the 9/11 attacks as "an act of 'mass murder, pure and simple'". Condemning the attacks, he has also stated "Islam was hijacked ... on that plane as an innocent victim".The Guardian newspaper in the United Kingdom reported that he "is arguably the west's most influential Islamic scholar" and added that "many Muslims find his views hard to stomach."

Hamza Yusuf was born to two academics in Washington State and raised in Northern California. In 1977, he became Muslim and subsequently traveled to the Muslim world and studied for ten years in the United Arab Emirates, Saudi Arabia, as well as North and West Africa. Hamza Yusuf spent four years studying in the United Arab Emirates and elsewhere in the Middle East. Later he traveled to West Africa and studied in Mauritania, Medina, Algeria, and Morocco under such scholars as Murabit al Haaj; Baya bin Salik, head of the Islamic court in Al-'Ain, United Arab Emirates; Muhammad Shaybani, Mufti of Abu Dhabi; Hamad al-Wali; and Muhammad al-Fatrati of Al Azhar University in Cairo, Egypt.^{[citation needed]} After more than a decade abroad, he returned to the United States and earned degrees in nursing from Imperial Valley College and religious studies at San José State University.^{[citation needed]}