Ijmaʿ (الإجماع) is a term in Islamic legal theory (uṣūl al-fiqh) referring to the consensus of qualified scholars (mujtahidun) on a point of religious law. Alongside the Qur'an, the Sunna, and analogical reasoning (qiyas), ijma is traditionally counted among the four primary sources of Islamic jurisprudence in Sunni legal theory, though its precise definition, scope, and binding force are subjects of substantial disagreement among jurists and schools. Definitions vary as to whose agreement counts (all Muslims, all scholars, scholars of a particular era or region), what subject matter it covers, and how such agreement is identified and verified; these contested points are addressed further at ijma-definition-debate and related pages.
Classical jurists developed several competing accounts of ijma. Some held that only the consensus of the companions of Muhammad (ṣaḥaba) carries full authority, while others extended the concept to the consensus of jurists in any generation. A further distinction is drawn between explicit consensus (ijma sarih), in which scholars openly state agreement, and tacit consensus (ijma sukuti), inferred from the absence of recorded dissent. Jurists have also disputed whether ijma, once established, is reversible by later generations, and whether it can address matters not already governed by clear scriptural text. The Zahiri school, associated with jurists such as Ibn Hazm, restricted recognized ijma to the consensus of the companions alone, rejecting broader or later claims of scholarly consensus as a valid independent source of law - a position discussed at ijma-zahiri-viewpoint.
Modern scholarship, including both reformist Muslim thought and Western academic studies of Islamic law, has further debated whether claims of ijma in classical legal texts reflect genuine, verifiable agreement or retrospective rhetorical claims used to settle disputed questions. This has implications for debates over the use of ijma as a vehicle for legal change in the present day, discussed further at ijma-history.