This study aims to define a dynasty that had an important role in the history of Oman, which is the Al Julanda dynasty that has been considered to be one of the first families which governed Oman before Islam. It also tracks their role in history until the mid-third century AH/ mid-ninth century AD. With an aim to study this dynasty in an objective way, the researcher depended on a number of primary sources, some modern references, a historical approach that is based on the description and analysis of historical allounts and applied, comparing them with the views of modern historians on the subject. The study consists of an introduction, a preface, three chapters, a conclusion and appendices. The introduction tackles the importance of the study, while the preface discusses the historical names of Oman and introduces the Al-Julanda dynasty. The chapters are: Chapter I, which follows Al Julanda dynasty before Islam and until the end of the Rashidi Caliphate (40 AH / 660 AD), Chapter II focuses on their relationship with the Umayyad ştate (41 AH / 661 AD-132 AH/ 750 AD) and the third Chapter discusses the role of the Al Julanda dynasty duting the reign of the Abbasid state (132 AH 1749AD-237 AH / 851 AD). There are several findings of the study, which include: Firstly: The name of Julanda was attributed to two families; one is Julanda bin Almstkbir that is linked with Maawlah Bin Shams, and the second family is Julanda bin Karkar that is linked to Malik bin Faham. Secondly: The territorial area of Oman was widened under the reign of Abd al-'Izz bin Maawlah bin Shams in the fourth and fifth century AD. to includ Bahrain and Yamama. Thirdly: The relation bety Julanda dynasty and The Sassanid Persian Empire before Islam was characterized by the truce, which allowed Persians to keep a garrison of about four thousand soldiers and a Persian governor in Oman and dominate the coastal areas, while Al-Julandas dominate the desert, mountains and the outskirts of Oman. Fourthly: The study discusses how Al Julanda's embraced of Islam, and the honorable role they played in the (Ridda) Apostasy wars and the Islamic conquests. Finally how Jeffer, Abd, and Abad continued as rulers of Oman during the reign of the Caliphs.