叩头是东亚一种传统仪式和礼节，又称为磕头，日本称为土下座。行此礼的人以双膝跪地，以头触地。用以表示高度的忠诚和尊敬。这种仪式本来用于人类对神佛，子女对父母、祖先，或犯上严重错误时道歉。

康有为在《拟免跪拜诏》中对中国君臣礼仪的演变总结道：“汉制，皇帝为丞相起，晋、六朝及唐，君臣皆坐。宋乃立，惟元乃跪，后世从之。” 因此，元朝蒙古人将佛教向神跪拜的仪式世俗化，跪拜转化为朝臣觐见皇帝的礼仪，到明王朝，皇权更盛，因而续承元朝之礼。秦之后，残酷的人殉已经消失；而明代朱元璋重用活人殉葬，也将跪拜仪式化，并时常在朝廷以廷杖之刑处罚大臣。 清代废弃了廷杖，但保留明朝已定型的跪拜仪式，包括人子对祖先，普罗大众对官员，下属对于长官，臣子对君主的礼仪。这种礼仪，在清朝近现代与其他国家如英国外交官员接触时，常引起外交礼仪上的重大争议 。

Kowtow, which is borrowed from kau tau in Cantonese (koutou in Mandarin Chinese), is the act of deep respect shown by prostration, that is, kneeling and bowing so low as to have one's head touching the ground. An alternative Chinese term is ketou; however, the meaning is somewhat altered: kou (叩) has the general meaning of knock, whereas ke (磕) has the general meaning of "touch upon (a surface)", tou (頭) meaning head.