Simnas (pronunciation (help·info); Polish: Simno; Russian: Симно; Yiddish: סימנע) is a city within the Alytus district municipality, Lithuania. It is located 23 km (14 mi) west of Alytus.
Simnas was first mentioned in written sources in 1494 as Simnas manor, owned by grand duke of Lithuania. In 1520 construction started of renaissance styled Simnas Church, which is the oldest currently heritage listed building in Suvalkija.
In 1626 duke Sigismund Vasa granted Simnas Magdeburg rights which it lost in 1776. First parish school in the town was founded in 18th century, while 19th century seen Simnas rise as an important local merchant hub.
On September 12, 1941, 414 Jews were murdered: 68 men, 197 women and 149 children by an Einsatzgruppen in a mass execution. A memorial is built on the site of the massacre.
In 1901, the total population was 1870, of which 944 were Jews and 926 were Poles. The religious makeup was half Jewish and half Roman Catholic.