逆行卡农（拉丁语：Canon Cancrizans，英语：Crab Cannon）是两个同时播放, 并且是互相相反于对方的声部, 类似于回文。逆行卡农原本是指一种由一条旋律从尾向头逆向模仿另一旋律所构成的卡农曲（例如 FABACEAE <=> EAECABAF）。约翰·塞巴斯蒂安·巴赫所作的《音乐的奉献》中有其中一个出名的例子, 叧外也有一首逆行倒影卡农（"Quaerendo invenietis"), 不仅两条旋律互相逆行,音高也是互相相反的。非音乐内容（Non-musical Contexts）这个用语被侯世达所着的哥德尔、埃舍尔、巴赫一书所普及。

A crab canon—also known by the Latin form of the name, canon cancrizans—is an arrangement of two musical lines that are complementary and backward, similar to a palindrome. Originally it is a musical term for a kind of canon in which one line is reversed in time from the other (e.g. FABACEAE played simultaneously with EAECABAF). A famous example is found in J. S. Bach's The Musical Offering, which also contains a canon ("Quaerendo invenietis") combining retrogression with inversion, i.e., the music is turned upside down by one player, which is a table canon.