Svencionys is a city located 84 kilometers (52 mi) north of Vilnius in Lithuania. It is the capital of the Švenčionys district municipality. As of 2005, it had population of 5,658 of which about one-third is part of the Polish minority in Lithuania. One of the oldest towns in the Grand Duchy of Lithuania, the settlement was a major center of Nalšia. Grand Duke Vytautas brought Lipka Tatars to the town and built a Catholic church in 1414.
The city grew during the 14–16th centuries when it was the site of a local court and monastery. Since 1801 the town was part of the Russian Vilna Governorate. It grew significantly after completion of the nearby Saint Petersburg – Warsaw Railway in 1862, but eventually lost competition to Svencionėliai, which grew around the train station. Around the turn to the 20th century the town had one Greek Orhodox church and one Roman Catholic church.