Kowtow (simplified Chinese: 叩头; traditional Chinese: 叩頭; pinyin: kòu tóu; Cantonese: kau tàuh, Vietnamese: khấu đầu) is the act of deep respect shown by kneeling and bowing so low as to have one's head touching the ground. An alternative Chinese term is ketou (simplified Chinese: 磕头; traditional Chinese: 磕頭; pinyin: Kētóu); however, the meaning is somewhat altered: kòu originally meant "knock with reverence",[citation needed] whereas kē has the general meaning of "touch upon (a surface)".[citation needed]

In Han Chinese culture, the kowtow is the highest sign of reverence. It was widely used to show reverence for one's elders, superiors, and especially the Emperor, as well as for religious and cultural objects of worship. In modern times, usage of the kowtow has become much reduced.