Piotrków Trybunalski (pyô`tərko͞of trĭbo͞onäl`skē), Rus. Petrokov, Ger. Petrikau, city (1991 est. pop. 81,300), Łódzkie prov., central Poland. A textile center, it also manufactures wood and glass products. One of Poland's oldest cities, it was first mentioned in 1217 and became the seat of several Polish diets (1347–1578) and tribunals (1578–1792). The city passed (1815) to Russia and was (1867–1915) the capital of Petrokov province. It reverted to Poland in 1919. Piotrków Trybunalski has several old churches and the ruins of a castle built by Casimir the Great.