球囊菌门（学名：Glomeromycota，AM fungi），又称聚合菌门、锈球菌门，是真菌界的七个门之一，目前约已发现400种生物。聚合菌可构成陆生植物的丛枝菌根（arbuscular mycorrhizas, AM），这种共生构造可协助植物吸收土壤中的无机盐，并据信是早期植物能适应陆地环境的重要关键。超过八成的维管束植物都有由球囊菌构成的丛枝菌根，且在苔藓植物等没有真实根部构造的植物中亦有树状菌根，可见丛枝菌根在陆地生态系的重要性。

Glomeromycota (informally glomeromycetes) is one of seven currently recognized divisions within the kingdom Fungi, with approximately 230 described species. Members of the Glomeromycota form arbuscular mycorrhizas (AMs) with the roots or thalli (e.g. in bryophytes) of land plants. Geosiphon pyriformis forms an endocytobiotic association with Nostoc cyanobacteria. AM formation has not yet been shown for all species. The majority of evidence shows that the Glomeromycota are symbionts with land plants (Nostoc in the case of Geosiphon) for carbon and energy, but there is recent circumstantial evidence that some species may be able to lead an independent existence. The arbuscular mycorrhizal species are terrestrial and widely distributed in soils worldwide where they form symbioses with the roots of the majority of plant species (>80%). They can also be found in wetlands, including salt-marshes, and associated with epiphytic plants.