The Kedayan (also known as Kadayan, Kadaian or Kadyan) are an ethnic group residing in Brunei, Labuan, Sabah, and parts of Sarawak on the island of Borneo. The Kedayan language (ISO 639-3: kxd) is the de facto national language of Brunei and bears a similarity to Brunei Malay, which is spoken by more than 530,000 people in Brunei, 46,500 in Sabah and 37,000 in Sarawak. In Sabah, the Kedayan mainly live in the cities of Sipitang, Beaufort, Kuala Penyu and Papar. In Sarawak, the Kedayans mostly reside in Lawas, Limbang, Miri and the Sibuti area. The Kedayan people are also regarded as a sub-ethnic group of the Klemantan Dayak people.
The origins of the Kedayans are uncertain. Some of them believe that their people were originally from Java, which they left during Bolkiah reign. Due to the Sultan's fame as a sea captain and voyager, he was well-known to the people of Java, Sumatra and the Philippines. It is believed that when the Sultan anchored in the island of Java, he became interested in the agricultural techniques adopted there. Accordingly, the Sultan brought some of the Javanese farmers back to his country to adopt the techniques. The farmers later interacted and were inter-married with the local Bruneian Malay people, giving birth to the Kedayan ethnicity. Today, most Kedayans are Muslims and they have accepted Islam since the Islamic era of the Sultanate of Brunei. Furthermore, they have also adopted Malay culture. The Kedayans are recognized as one of the indigenous people of Borneo, and they are experts in making traditional medicines. The Kedayans are also well-known for their medicinal plants, which they grow to treat a wide range of ailments, and to make tonics.
The language of one of the indigenous tribes, Banjar, in Kutai, Kalimantan, is also said to be more than 90% similar to the Kedayan language, despite the fact they do not refer to themselves as Kedayans. Both the Kedayans and Banjarese are related to a certain extent because of their similar language.