Dionisia is a genus of parasitic alveolates belonging to the phylum Apicomplexa.

The type species of this genus is Dionisia bunoi.

The schizonts develop in the lumen of the liver blood vessels inside a greatly hypertrophied host cell.

They remain moderate in size and their cytoplasm is not intensely basophilic as is usually in the young stages of other mammalian Haemosporidia.

These parasites are found in Gabon, Africa.