The Mat Salleh Rebellion was a series of major armed disturbances against the British North Borneo Chartered Company administration in North Borneo, now the Malaysian state of Sabah. It was instigated by Datu Muhammad Salleh (also known as Mat Salleh [ms]), a local chief from the Lingkabo district and Sugut River. He led the rebellion between 1894 until his death in Tambunan in 1900. The rebellion then continued on for another five years until 1905.

His revolts were widely supported by the local communities and affected a large geographical area from Sandakan, across Gaya Island, including the interior, especially Tambunan. His most notable uprising occurred at midnight on 9 July 1897, when he led his followers to successfully attack a major colonial settlement on Gaya Island.

Mat Salleh was born in Inanam, Jesselton (present-day Kota Kinabalu). His father was Datu Balu, a traditional leader in Inanam and a Suluk or Tausug. His mother was of Bajau descent. He had three siblings: Ali, Badin and Bolong. The family moved to Sugut, which unlike Inanam, was in the North Borneo Chartered Company's concession but since the abandonment of its tobacco estates, it had reportedly been "left largely to its own devices", and enjoyed relative autonomy. There, Datu Bulu assumed a local leadership position along part of the Sugut River on the eastern coast of North Borneo.

Later in his life, Mat Salleh married a Sulu princess named Dayang Bandang. She was related to the Sultan of Sulu's family and her village was at Penggalaban, Paitan. He later inherited his father's local leadership position as the village chieftain in the Lingkabau district and Sungei Sugut.

Mat Salleh was often physically described as slender and tall, with pockmarked features. He was also well known as a mysterious and intelligent man, with a commanding personality and presence. He was well-respected and his great tactical skills were renowned among the local communities.

His mixed parentage and role as a traditional local leader which he had inherited from his father contributed to his significant Bajau and Suluk following. Also, his marriage to Dayang Bandang, who was related to the ruling family in Sulu helped him win more supporters.

However, his wide support not only came from his family affiliations and connections. He was also able to garner supporters from Dusun communities spread over a sizeable area in North Borneo and had the Tagahas communities as allies, among others. He was skilled at connecting with and uniting other communities, making him a great personage among the multi-ethnic indigenous people. For example, some accounts claim that he used and married various symbols of authority and mysticism that the different communities could relate with to attest to his leadership position and military prowess.

The large areas where his support came from proved instrumental in ensuring the initial success of his revolt as these areas were available to provide power bases, supplies and construction of forts. This also implied that he and his army had ample mobility between forts and bases, which explains their repeated evasion of the company's troops. From 1895 to 1897, he had at his disposal at least six forts which were well-prepared with resources and manpower that he could mobilise at short notice.