We diagnosed renal coccidiosis in two of five Great-horned Owls (Bubo virginianus) examined in eastern Tennessee, US, 2007–13. Histopathologic examination of the kidneys revealed multifocal mild-to-moderate dilation and epithelial hyperplasia of collecting ducts. Renal collecting duct epithelial cells contained intracytoplasmic microgametocytes, macrogametocytes, and sporulating and sporulated oocysts. Renal coccidiosis in affected birds did not result in significant inflammation. Sequence analysis of the amplified partial 18S short subunit ribosomal RNA coding region from examination of formalin fixed tissue by using PCR disclosed a 93% identity to Eimeria reichenowi in GenBank, suggesting a novel Eimeria sp.