Canthium species were predominantly found in Southeast Asia, especially in Thailand and the Philippines.

[2] A small number of species was found in India, Sri Lanka, and Bangladesh.

Only a limited number of species were found on the African continent, especially in Southern and East Africa.

[2] Canthium is a member of Vanguerieae, a tribe that is monophyletic and easily recognized morphologically, but in which generic boundaries were, for a long time, very unclear.

[14] In 2016, two Canthium species endemic to the Philippines were transferred to a genus of their own, Kanapia.