A new fungus of the Glomeraceae found in the rhizosphere of Agave sisalana is described under the epithet Septoglomus titan. It forms large glomerospores, (243–)265 × 325(–400) μm in diameter. They generally are subglobose and have three spore wall layers: a semi-persistent short lived sub-hyaline to yellow-brown outer layer (0.5–1.4 μm thick), an adherent smooth light-yellow to orange-brown middle layer (2.5–5.1 μm), and a laminate smooth thick orange brown to dark red brown innermost layer (12.8–19.2 μm). Spore size and colors of the spore wall layers separate this species from other yellow-brown to dark-brown species.