Microsporidia are a widespread group of microorganisms that originally were considered Protozoa but now have been placed in a separate group with features of fungi and protozoa. They infect a range of tissues in both invertebrates and vertebrates. A microsporidian infecting the midgut and fat body cells of a beetle triungulin in mid-Cretaceous Burmese amber is described as Microsporidium burmanicum sp. nov. Stages of schizogony and sporogony with developing spores in pansporoblasts occur in the infected triungulin. This is the first record of a fossil Microsporidia.