Seredzius is a town in Lithuania on the right bank of the Neman River near its confluence with the Dubysa River. According to the 2001 census, it had a population of 749. Southeast of the town, archaeologists discovered graves from the 3rd–4th centuries. The town also has a large hillfort, identified by historian Zenonas Ivinskis as Pieštvė, which was attacked by the Teutonic Knights numerous times in the late 13th and early 14th centuries.
According to the Palemonids legend, noble refugees from the Roman Empire settled on the hill, now named after Palemon, and established the Grand Duchy of Lithuania. After the Battle of Grunwald, the location lost its military purpose and became private property of the Sapieha family. The Sapiehas built a residential palace, which did not survive. The town's first Catholic church was built around 1608–1612. The church was destroyed in 1829 after a landslide caused by extensive flooding. The residents built a wooden church, which was replaced by a Neo-Renaissance church dedicated to John the Baptist in 1913.