刘完素（12世纪约1100年－1180年），字守真，自号通元处士，河间（今河北河间市）人，世称刘河间。金元四大医学家之一，研究五运六气，为“寒凉派”的创始人。

发挥《内经》理论，提倡火热论，并重视针灸治法，临床施治重视井穴、原穴。并喜用五腧穴，以火热论思想指导针灸临床，形成了以清热泻火为基点的针灸学术思想，对金元以后的医家影响很大。因创制不少治疗伤寒热病的方剂，故后世称他为“寒凉派”。

刘完素的著作有：《黄帝素问宣明论方》、《素问玄机原病式》、《宣明内方》、《内经运气要旨论》、《伤寒直格》、《伤寒标本心法类萃》、《三消论》、《素问药注》、《医方精要》。

Liu Wansu (Chinese:劉完素; pinyin:Líu Wánsù; 1110–1200) was a Jin dynasty Chinese physician. He observed the high frequency of fever and inflammation in serious diseases and promoted the idea of using herbs of cooling nature to treat these conditions. This was a step in the opposite direction of many of his predecessors, who focused on using warming herbs. This work had much influence on the later concept of "wen bing" or epidemic febrile diseases, which corresponded to (and preceded) the Western concept of contagious disease. He also undertook a detailed study of the Nei Ching Su Wen [Nei Jing Su Wen], describing the etiology of disease in relation to the teachings of that famous text.