Caolan, sometimes Man Cao Lan, is a Tai language of northern Vietnam. It is spoken by the Cao Lan subgroup of the San Chay people; the Sán Chay proper speak a form of Chinese. According to Pittayaporn (2009), it is closest to the Chongzuo and Shangsi Zhuang across the border in China, both of which are lumped under the apparently polyphyletic Yongnan Zhuang by Ethnologue. Together, Caolan, Chongzuo, and Shangsi form a primary branch of the Tai languages (Pittayaporn 2009).