硫循环（英语：Sulfur cycle）是一些过程的集合，其中包括硫在矿物质（包括水体）和生命系统之间移动进出过程。这样的生物地质化学循环对于地质学是重要的，因为它们会影响多种矿物质。生物地质化学循环对于生命也很重要，因为硫是一个基本元素，是作为许多蛋白质​​和辅因子的组成成分。

硫循环的步骤是：

The sulfur cycle is the collection of processes by which sulfur moves to and from minerals (including the waterways) and living systems. Such biogeochemical cycles are important in geology because they affect many minerals. Biochemical cycles are also important for life because sulfur is an essential element, being a constituent of many proteins and cofactors.