In biology, a microspore is a small spore as contrasted to the larger megaspore.
In botany, microspores develop into male gametophytes, whereas megaspores develop into female gametophytes. The combination of megaspores and microspores is found only in heterosporous organisms. In seed plants the microspores give rise to the pollen grains, and the megaspores are formed within the developing seed. Most plants that reproduce by spore without seed only produce one class of spore. In the ferns, the only heterosporous plants are aquatic or semi-aquatic, including the genera Marsilea, Regnellidium, Pilularia, Salvinia, and Azolla. This condition is also known in the lycopod genus Selaginella and in the quillwort genus Isoëtes.
In zoology, the small swarm-spores of Sarcodina are called microspores.