Hirnant Limestone
Stratigraphic range: Hirnantian ~446–444 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Formation
Lithology
Primary	Limestone
Location
Coordinates	52°54′N 3°36′W / 52.9°N 3.6°W / 52.9; -3.6
Approximate paleocoordinates	38°06′S 16°54′W / 38.1°S 16.9°W / -38.1; -16.9
Country	England, Wales
Hirnant Limestone (the United Kingdom) Show map of the United Kingdom Hirnant Limestone (Wales) Show map of Wales

The Hirnant Limestone is an old name for a geologic formation in England and Wales, defining the Hirnantian. It preserves fossils dating back to the Ordovician period.^[1] It is now classified as the Hirnant Limestone Member of the Foel Y Ddinas Mudstones Formation.^[2]

• List of fossiliferous stratigraphic units in Wales

• J. T. Temple. 1965. Upper Ordovician-Brachiopods from Poland and Britain. Acta Paleontologica Polonica 10:379-450
• J. W. Salter (5 May 1867). "Bala and Hirnant Limestone". Geological Magazine. Vol. 4, no. 3. pp. 233–234. doi:10.1017/S0016756800204548.
• Adam Sedgwick (1848). On the older Palaeozoic (protozoic) rocks of North Wales in Proc.Geol.Soc, London, Vol.4.