Sayyid Mashhur bin Muhammad Al-Shahab (commonly also known as Syarif Masahor or Sharif Masahor in Malayan contexts) (died 1890 in Selangor) was a famous Malay warrior of Hadhrami descent in Sarikei, Sarawak state, Malaysia during the Brooke White Rajahs era in that state. Before the arrival of James Brooke, he was a powerful member who ruled and, in the past, like Datu Patinggi Abdul Gapur, he was very influential and respected due to both his charisma in uniting the people of different races and beliefs, and also due to his lineage. James Brooke's expansion policy caused disturbance in many parts of Borneo. In the initial agreement between James Brooke and the Sultan of Brunei, Sarawak was only a territory which stretched from Tanjung Datu to Maong River (Sungai Maong). Syarif's territory was far away from the designated area. Brooke's encroachment into local leaders' territory caused many locals to rebel, including Syarif Masahor. James Brooke departed for England at the end of 1857, leaving his nephew Charles behind to monitor the rule. This allowed Masahor to put his plans into action. In July 1859, Masahor and his army attacked Brooke's outpost near Bukit Rejang in Kanowit.