The Duchy of Legnica or Duchy of Liegnitz is one of the Duchies of Silesia.

Its capital is Legnica (Liegnitz) in Lower Silesia.Legnica Castle had become a residence of the Silesian dukes in 1163 and from 1248 is the seat of a principality in its own right, ruled by the Silesian branch of the Piast dynasty until 1675.

Formed by Bolesław II the Bald, Duke of Lower Silesia at Wrocław, Legnica shares the fate of most of the others Silesian duchies, falling into Bohemian, Austrian and eventually—after the First Silesian War—Prussian spheres of influence.