Sieradz, city, Łódzkie województwo (province), central Poland.
Sieradz is one of the oldest cities in Poland. About 1025 a fortified township was founded on the present site. Although reinforced in the 14th century, the fortress town was destroyed by Swedish invaders. Surviving examples of historic architecture and art in the city, dating as far back as the 14th century, include the Dominican church with a monastery, the Market Square, and the Royal House (Królewska Kamienica); there is also a regional museum. The urban economy is based on the manufacture of knitted textiles and farm machinery and on food processing. Pop. (2011) 43,903.