Thymus jalasianus Stoyanov & Marinov (Lamiaceae), a distinctive species in the section Hyphodromi subsection Serpyllastrum, is described as new to science from the Eastern Rhodope Mountains, southern Bulgaria. The species morphologically resembles T. zygioides and T. granatensis by its prostrate habit, woody radicant stems, holotrichous flowering stems and narrowly spathulate leaves. Thymus jalasianus can be distinguished by a combination of its small globose strobilus-like inflorescence, not elongated in fruit, and remarkable imbricate, rhomboid to suborbicular, ± navicular, scarious bracts, enclosing calyces before and after anthesis. Thymus bracteosus is excluded from the Bulgarian flora based on revised specimens that turned out to belong to T. jalasianus.