分解作用，又称腐烂、腐败，是指动物蛋白质及其有关之有机物分解成无机物，而且回到大自然物质循环的过程，特别是由缺氧微生物和腐化细菌。分解是一个大自然经常进行且非常重要的过程。腐败物通常导致胺物分解时出现如腐肉碱和尸碱等的生物碱，具有腐败气味。在生物学方面，腐烂和发酵在某程度上有少许相似，基本上二者同样意味着允许有机物质转变或分解成另一些物质。

腐败物的腐烂的速度取决环境和质量。当然，还有许多因素影响着，例如天气、曝光和地点。

Decomposition is the process by which organic substances are broken down into a much simpler form of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death. Animals, such as worms, also help decompose the organic materials. Organisms that do this are known as decomposers. Although no two organisms decompose in the same way, they all undergo the same sequential stages of decomposition. The science which studies decomposition is generally referred to as taphonomy from the Greek word τάφος taphos, meaning tomb.