Ilz is a municipality in the district of Hartberg-Fürstenfeld in Styria, Austria. It lies at approximately 47° 05' N, 15° 56' E, at about 300 metres above sea level, on the left bank of the river Ilz, in the roughly one-kilometre-wide Ilz valley. It is situated 43 kilometres east of Graz, 19 kilometres east of Gleisdorf and 13 kilometres west of Fürstenfeld.
The settlement was first named in a writ issued on 14 October 1265 in Graz by Herbord of Fullnstein, who was sewer to Bishop Bruno of Olmütz. The writ mentions a witness, Dominus Wernherus de Ylnz, probably the vicar of the town.