Hardsyssel or Harsyssel is a traditional district and an ancient syssel in Denmark, forming the western part of central Jutland.
The biggest towns in Hardsyssel are Herning, Holstebro, Struer, Ringkøbing, Skjern, Lemvig and Ikast.
The name is believed to be derived from the Germanic stem of the Harudes, as are the county and the traditional district of Hordaland and Hardanger in Norway.
The landscape is flatter and more open than that of eastern Denmark, marked by sandy soil, heath and some conifer plantations.
After Denmark's loss of Slesvig and Holstein in 1864, it was decided to claim much of the infertile land for agriculture, but some of the heaths remain.