The ultimate authority in Shi?i Islam rests with the Imams. Much has been written about what legitimates an Imam and confirms his authority. This paper looks at the role ascribed to Umm Salamah in legitimating three of the twelve Imams, most importantly ?Ali, his son al-Husayn and his son Zayn al-?Abidin. It also looks at how she kept the na??, designating the Imams as the rightful and legitimate authority, safe until they were able to retrieve it to assume their rightful position and enact their authority. The paper is in three parts and starts by looking at the term ahl al-bayt and its interpretations, as it shapes the Imamate and is a term of contention between Sunnis and Shi?is. This is followed by introducing Umm Salamah and the reasons she was particularly revered in Shi?i traditions, as well as her main narrations from the Prophet in support of the ahl al-bayt in general and ?Ali in particular, such as for example ?ad?th al-kis??, ?ad?th Ghad?r Khumm, ?ad?th al-manzalah, as well as ?ad?th al-thaqalayn. These reports emphasize ?Ali’s exclusive rights to succeed the Prophet, and therefore by extension the right of his progeny to the Imamate. Finally, the last part looks at the Imam’s authority and the necessity of a na??, designating the Imam as legitimate and Umm Salamah’s role that earned her the honorific ??fi?at al-na?? (‘Keeper of the na??’). The paper concludes that while the Imamate was a distinctly male prerogative, the na?? granting legitimacy was delivered to them by a woman, whether it was Umm Salamah as in the majority of reports, or Fatimah bt. al-Husayn, or Zaynab bt. ?Ali, as found in some solitary reports. In serving this crucial role, the women of ahl al-bayt, including the Prophet’s wife Umm Salmah in particular, come to share in a significant fashion in legitimating the authority of the Imams.