Blood specimens were received from five cases in which young adult giraffe, from different geographic origins in South Africa, showed sudden onset of disease and subsequently died. Additional specimens from two translocated giraffe, as well as one specimen from a roan antelope, were also included in the study. Blood slides from some of these animals showed the presence of piroplasms. DNA was extracted; the V4 hypervariable region of the 18S rRNA gene amplified and analyzed using the Reverse Line Blot (RLB) hybridization assay. PCR products failed to hybridize with any of the Babesia or Theileria species-specific probes, and only hybridized with the Babesia/Theileria genus-specific probe suggesting the presence of a novel species or variant of a species. Full-length 18S rDNA was amplified, cloned and the recombinants were sequenced. 18S rRNA gene sequence similarity analysis revealed the presence of novel piroplasm species in both healthy giraffe and a roan antelope and clinically sick or dead giraffe. Phylogenetic analysis grouped five of these organisms in the Babesia sensu stricto clade and three in the Theileria sensu stricto clade. Although parasites were observed in blood smears, there is no direct evidence that piroplasmosis caused the death of five giraffe, although it certainly seems to be likely.