The 20th Century Mandailing Ulama Tradition: Dedication and Works of Yusuf Ahmad Lubis (1912-1980). This article examines the dedication and works of Yusuf Ahmad Lubis. This figure is worth studying given his significant contribution and position in the Al Washliyah organization and who later become the Acting Chair of the North Sumatra Ulema Council, but it is still academically neglected. This article is the result of a literature study with a historical approach. The findings of this article are that Yusuf Ahmad Lubis, although he had never studied religion in Haramain, but had an intellectual network with Makkah scholars through his two most famous teachers: Sheikh Hasan Maksum and Sheikh Muhammad Yunus. His mastery in the Islamic religious sciences is dedicated to the people and nation through Al Jam'iyatulWashliyah. He also left dozens of works behind him in various fields of Islam. It is interesting that he has the ability in the field of comparative religion, and this ability has made him successful in carrying out the mission of Islamization on Christian bases in North Sumatra. His opposition to the Jalaluddin order and the Ahmadiyya sect increasingly shows that he wants to protect the faith of Muslims. This study successfully revealed the profile of a universalist ulama in terms of science and also still critical of ideological differences.