Piétrain is a Belgian breed of domestic pig. It is native to Wallonia, and takes its name from the village of Piétrain in the municipality of Jodoigne in Walloon Brabant, in northern Wallonia. It first appeared in about 1920 and received recognition as a breed in 1950. Its origins are not clear; it has been suggested that the farmers of Piétrain may have recognised, and selectively bred for, a genetic mutation causing muscular hypertrophy.
From about 1960, the Piétrain was also reared in Germany, principally in Baden-Württemberg, Nordrhein-Westfalen and Schleswig-Holstein; it is used as a sire for cross-breeding.
The breed was improved by researchers at the Université de Liège in 2004.