This study aimed to trace the history of endowment in the Town of Rustaq during the historical era (12th -14th AD/ 18th -20th Century AD), and its effect on social and cultural life of the town. The researcher adopted the historical, descriptive analytical methodology that focuses on investigation and examination, by review of the documentary material represented in the copies of Aflaj and endowment wills and deeds, and conclusion and analysis of the historical facts from them, in addition to the bibliography, references, interviews and analysis of the information derived by them. The study was divided into an introduction, preface, four chapters and conclusion. Preface addressed the theoretical constants on endowment and its linguistic and terminological definition, its legality, pillars and types, and endowment in the Ibadite perspective as well as the forms that have been used. Chapter one addressed the historical development of endowment in Rustaq Town, and its sources and types. Chapter two investigated regulation and management of endowment in Rustaq Town and the risks that it encountered. Chapter three elaborated the types of social endowment and its effect on social life and Rustaq women contribution to endowment. Chapter four focused on the types of cultural endowment by examination of the religious endowment and scientific endowment and their effects on cultural life in Rustaq Town. The study drew set of conclusions, mainly that it revealed the historical development of endowment in Rustaq and factors of its spread, sources and types, and how it is regulated, managed and documents as well as the risks that it encountered and the categories that participated in the endowment, including Rustaq women and their endowment contributions.