In this study, species of Thymus growing in Eskişehir have been morphologically investigated. Four Thymus species and altogether five taxa of which one is endemic were found to be native to the area. These are: T. sibthorpii Bentham, T. sipyleus Boiss., T. leucostomus Hausskn. & Velen. var. argillaceus Jalas and T. longicaulis C.Presl subsp. longicaulis var. subisophyllus (Borbas) Jalas, subsp. chaubardii (Boiss. & Heldr. ex Reichb. fil) Jalas var. chaubardii. T. leucostomus is an endemic species to Turkey. In morphological studies, detailed descriptions of the species and characteristic features are given. General appearance of plants, leaf, bract, flower, calyx, corolla and fruit shapes have also presented. All species were gynodioecious. Our findings abaut T. sibthorpii and T. sipyleus are contradict those of Jalas in Flora of Turkey. It is apparent that taxonomic studies of these species should still be persued further. T. longicaulis subsp. chaubardii var. chaubardii is a new record for the B3 square. Additionally, T. sipyleus and T. longicaulis subsp. longicaulis var. subisophyllus has been collected in the vicinity of Eskişehir for the first time compared to the records in Flora of Turkey. T. leucostomus var. argillaceus has been observed to be the most widespread species in Eskişhir.