The name Kelantan is said to be a corruption of gelam hutan, i.e. the Malay name for the cajuput, or swamp tea tree (Melaleuca leucadendron). Other theories claim the name comes from the Malay word kilatan, 'shiny/glittery' or kolam tanah, 'clay pool'.
The early history of Kelantan is rather obscure, but archaeological finds indicate traces of human settlement dating to prehistoric times. Early Kelantan had links to the Funan Kingdom, the Khmer Empire, Srivijaya and Siam. Around 1411, Raja Kumar, the ruler of Kelantan, became independent of Siam, and Kelantan became an important centre of trade by the end of the 15th century. In 1499, Kelantan became a vassal state of the Malacca Sultanate. With the fall of Malacca in 1511, Kelantan was divided up and ruled by petty chieftains. With the conquest by Siam in 1603, most of these petty Kelantan chiefs became subject to Patani. Around 1760, a petty chieftain of Kubang Labu in Kelantan succeeded in unifying the territory of the present Kelantan. Shortly thereafter, in 1764, Long Yunos seized the throne and proclaimed himself Raja of Kelantan. However, with his death, Kelantan came under the influence of neighboring Terengganu.
In 1800, Raja Muhammad declared himself as the first Sultan of Kelantan. In 1812, he broke from Terengganu's influence and became a separate tributary of Siam. In the 1820s, Kelantan was one of the most populous and prosperous states in the Malay Peninsula, having avoided the wars and disputes which plagued the southern and western states. Siam continued to play an important role in Kelantan throughout the 19th century.
Under the terms of the Anglo-Siamese Treaty of 1909, Siam surrendered its claims over Kelantan, Terengganu, Kedah and Perlis to Great Britain, and Kelantan thus became one of the Unfederated Malay States with a British Adviser.
Kelantan was the first place in Malaya to be occupied by the Japanese, who invaded on December 8, 1941. During the Japanese occupation, Kelantan came again under control of Siam, but after the defeat of Japan in August 1945, Kelantan reverted to British rule.
Kelantan became part of the Federation of Malaya on February 1, 1948 and together with other states attained independence on August 31, 1957. On September 16, 1963, Kelantan became one of the component states of Malaysia.