Aspidothelium is a genus of lichen-forming fungi in the family Thelenellaceae. All species in the genus have a tropical distribution and are crustose with a photobiont partner. Most Aspidothelium species are foliicolous (leaf-dwelling), although some corticolous (bark-dwelling) species are known, as well as a single saxicolous (rock-dwelling) member.
The genus was circumscribed by Finnish lichenologist Edvard August Vainio in 1890. Historically, it has at times been considered as a synonym of genus Thelenella. Families in which the genus has previously been classified are the Verrucariaceae, Strigulaceae, and the Aspidotheliaceae, a monogeneric family circumscribed especially to contain this genus. Modern molecular phylogenetic analysis has shown its placement in the family Thelenellaceae, allied with the order Ostropales.
Aspidothelium is known for its production of that range in colour from whitish to pinkish or grey and are . These perithecia often exhibit wart-like, setae, or disc-like structures on their surface. Within the perithecia, dense and unbranched and can be found alongside clavate asci and colourless ascospores. These ascospores are typically in shape, and to transversely septate. Aspidothelium is particularly notable for its unique characteristic of producing fusiform ascospores with numerous transverse septa and short, broad cells.