Seseli L. is represented by 12 taxa (species and subspecies) in the Flora of Turkey. On the basis of morphological examination and field investigation, we have revised the genus Seseli in Turkey. The following are provided for each taxon: a description, along with the complete synonymy and notes on nomenclature, geographical distribution, habitat, IUCN conservation status assessment, and selected materials examined. Two new species from Turkey, Seseli marashica E. Dogan & H. Duman and S. serpentina B. L. Burtt ex H. Duman & E. Dogan, are also described. One taxon is reduced to synonymy: S. paphlagonicum Pimenov & Kljuykov is a synonym of S. gummiferum Pallas ex Smith. Moreover, one species is reduced to the rank of subspecies: S. corymbosum Boiss. & Heldr. ex Boiss. subsp. phrygium (Pimenov & Kljuykov) E. Dogan & H. Duman. According to the present revision, the genus contains 13 taxa (species and subspecies).