Mandailing Ulama at the Beginning of the 20th Century: Abdurrahman Sjihab's Religious and Political Movement (1910-1955). This study aims to examine the religious and political movements of Abdurrahman Sjihab. This study utilizes written sources that are then analyzed by content analysis methods. Despite the important role played by Abdurrahman Sjihab as one of the leaders of the Islamic religion who fought at the local and national level as a freedom fighter for the Republic of Indonesia, there has not been a study that covers his biobiography. This study finds that Abdurrahman Sjihab contributed to the efforts to fight, defend and contribute to the independence of the Republic of Indonesia. In the socio-religious field, he and his colleagues founded Al Jam'iyatul Washliyah, which is engaged in education, preaching and social affairs, and this effort was relatively successful in preparing militant Muslim resources. In the social political field, he on behalf of Al Washliyah fostered relations and established coordination with Islamic leaders at the local and national levels in the context of fighting for and filling Indonesian independence, and for this reason he became a Masjumi politician, a member of the Central Indonesian National Committee (KNIP) and member of the Provisional People's Representative Council (DPRS). This study is expected to nurture the biographical treasures of Muslim figures in the early days of Indonesian independence.