A da'i (Arabic: داعي dā‘ī [ˈdæːʕi(ː)], "inviter") is generally someone who engages in da'wah, the act of inviting people to Islam. But is more specifically an important religious office amongst the Isma'ili Shi'i Muslims, which has been held by important scholars through history.
In the Fatimid Caliphate era, the term dā'ī was used to refer to important religious leaders other than the hereditary Imams, and the Da'wah or "Mission" is a clerical-style organisation. Literally meaning "absolute missionary" or "unrestricted missionary", Da'i al-Mutlaq is nowadays the title of the head of the Dawoodi Bohra community.
Some of the greatest Ismaili Dais are: ( al-Qadi al-Nu'man (d. 974)