The spur-thighed tortoise (Testudo graeca) is an endangered Mediterranean tortoise that lives in North Africa, Southern Europe and Southwest Asia. In the wake of recent legislation making their keeping as domestic animals illegal, many of these animals have been returned to wildlife recovery centers in Spain. In the present study, a population of such tortoises showing signs of ocular disease and nasal discharge was examined for the presence of Chlamydia spp. Cloacal, conjunctival and/or choanal swabs were collected from 58 animals. Using a real-time PCR specific for the family Chlamydiaceae, 57/58 animals tested positive in at least one sample. While only a few samples proved positive for C. pecorum, sequencing of the 16S rRNA gene revealed a sequence identical to previously published sequences from specimens of German and Polish tortoises. Whole-genome sequences obtained from two conjunctival swab samples, as well as ANIb, TETRA values and a scheme based on 9 taxonomic marker genes revealed that the strain present in the Spanish tortoises represented a new yet non-classified species, with C. pecorum being its closest relative. We propose to designate the new species Candidatus Chlamydia testudinis.