分裂（英语：Fission）在生物学中是指一个细胞（或身体、种群或物种）分为两个或多个部分，以及这些部分再生为细胞（身体、种群或物种）。二分裂（英语：Binary fission）产生两个细胞、种群或物种等，而复分裂（英语：multiple fission）产生多于两个的细胞、种群或物种等。

In biology, fission is the division of a cell (or body, population, or species) into two or more parts and the regeneration of those parts into separate cells (bodies, populations, or species). Binary fission produces two separate cells, populations, species, etc., whereas multiple fission produces more than two cells, populations, species, etcetera