Užupis is a neighborhood in Vilnius, the capital of Lithuania, largely located in Vilnius' old town, a UNESCO World Heritage Site. Užupis means "on the other side of the river" in the Lithuanian language and refers to the Vilnia River. The name Vilnius was derived from the Vilnia. The district has been popular with artists for some time, and has been compared to Monmartre in Paris due to its bohemian atmosphere. The district houses art galleries, artists' workshops, and popular cafés. On April Fools Day, 1997, the district declared itself an independent republic (The Republic of Užupis), replete with an army of 12 personnel.

Užupis is quite small and isolated, being only about 148 acres (0.60 km²) in size. On one side it is separated from the Old Town by the Vilnia River, on the other there are steep hills, and on the third there is an industrial area built under the Soviet rule. The first bridges across the river were built in the 16th century, at which time the district's inhabitants were mostly Jewish.

The district contains the Bernardine Cemetary, one of the oldest in the city. Most of the district's Jewish population vanished during the Holocaust, and later even the old Jewish Cemetary would be destroyed by the Soviets. The houses left empty by the Holocaust were occupied by marginal elements of society, the homeless, and prostitutes. At the end of 19th century in Užupis there lived Felix Dzerzhinsky — and later Mikalojus Konstantinas Čiurlionis. Until Lithuania's declaration of independence in 1990, it was one of the most neglected areas in the city, containing many run-down houses, many without utilities. The region has been a common haunt of artists and bohemians since Soviet times, and even today many young artists are squatting in abandoned buildings near the Vilnia River.

They celebrate this independence annually on Užupis Day, which falls on April 1st. Artistic endeavours are the main preoccupation of the Republic and indeed the current President of the Republic of Užupis, Romas Lileikis, is himself a poet, musician, and film director. The first major initiative undertaken by the Republic after its foundation was to build a monument for Frank Zappa, in Vilnius.

Copies of the 41 articles of the Republic's constitution, in three languages, can be found affixed to a wall on Paupio street in the area. Some of these articles would be unremarkable in a constitution; for instance, Article 5 simply reads "Man has the right to individuality.". Others are more idiosyncratic. A typical example can be found in Articles 1 ("People have the right to live by the River Vilnelė, while the River Vilnelė has the right to flow past people."), 12 ("A dog has the right to be a dog.") and 37 ("People have the right to have no rights."), each of which makes an unusual apportionment of rights. There are a number of paired articles, such as Articles 16 ("People have the right to be happy.") and 17 ("People have the right to be unhappy.") which declare people's right to either do or not do something, according to their desire.

On April 4, 2002, a statue of an angle blowing a trumpet was unveiled in the main square. It was intended to symbolize the revival and artistic freedom of the district.