Mattesia is a genus of parasitic alveolates of the phylum Apicomplexa. Species in this genus infect insects (Coleoptera, Hymenoptera, Lepidoptera and Siphonaptera).

The genus was created in 1930 by Naville.^[1]

There are eight recognised species in this genus.

The type species is Mattesia geminata.

• M. alphitobii — lesser mealworm (Alphitobius diaperinus)
• M. dispora — Indianmeal moth (Plodia interpunctella)
• M. geminata — fire ant (Solenopsis geminata)
• M. grandis — boll weevil (Anthonomus grandis)
• M. orchopiae — flea (Orchopeas wickhami)
• M. oryzaephili — sawtoothed grain beetle (Oryzaephilus surinamensis)
• M. povolnyi — Eurasian sunflower moth (Homoeosoma nebulellum)
• M. trogodermae — Glabrous cabinet beetle (Trogoderma glabrum)

This genus is a synonym of Coelogregarina Ghélélovitch, 1948.

Mattesia bombi has been moved to a new genus — Apicystis bombi.