The Ustmylian Gorizont is a Lower Triassic biostratigraphic unit in Western Russia. The Ustmylian Gorizont is the youngest subunit of the Vetlugian Supergorizont, lying above the Sludkian Gorizont and below the Yarenskian Gorizont. It corresponds to the later part of the early Olenekian stage. Along with the Sludkian Gorizont, the Ustmylian Gorizont is encompassed by the "Wetlugasaurus fauna", named after a capitosaur amphibian index fossil. While the Sludkian is characterized by Wetlugasaurus angustifrons, the Ustmylian is characterized by Wetlugasaurus malachovi.