BIELITZ, a town of Poland in Silesia (Czech. Bilsko, Polish Bielsko), 4o m. S.E. of Ratibor. It is one of a series of towns in the border zone between the Carpathian mountains and the plain of Eastern Europe. It is situated on the river Biala a small tributary of the upper Wisla (Vistula), just opposite the town of Biala. Bielitz, founded in the i3th century, was an important fortified town in the 15th and 16th centuries. It has a castle associated with the Sulkowsky family in favour of whom the lord ship of Bielitz was raised to a duchy in 1752. It is an important weaving centre with much trade in woollens and linen. It also manufactures jute and machinery. After the war of 1914-18 Bielitz was in disputed territory and passed from Austrian to Polish hands as a result of the Treaty of St. Germain-en-Laye, Sept. I o, 1919.