Seredžius is a town in Lithuania, situated on the right bank of the Neman River near its confluence with Dubysa River. According to the 2001 census, it had population of 749.
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 a 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 a large flooding. The residents built a wooden church, which was replaced by a Neo-Renaissance John the Baptist church in 1913.
The town also had a large Jewish population prior to the Holocaust. In 1900 (when part of the Russian Empire) the town's Jewish population numbered 1,174. The Yiddish name for the city was סרעדניק (Srednik), corresponding to the Polish and Russian names Średniki and Средники (Sredniki).
Seredžius was the birthplace of the American singer, comedian, and actor Al Jolson, born into the town's Jewish community in 1886 as Asa Yoelson.