The national flag of Slovenia features three equal horizontal bands of white (top), blue, and red, with the Slovenian coat of arms located in the upper hoist side of the flag centered in the white and blue bands. The coat of arms is a shield with the image of Mount Triglav, Slovenia's highest peak, in white against a blue background at the centre; beneath it are two wavy blue lines representing the Adriatic Sea and local rivers, and above it are three six-pointed golden stars arranged in an inverted triangle which are taken from the coat of arms of the Counts of Celje, the great Slovenian dynastic house of the late 14th and early 15th centuries.

The flag's colours are considered to be Pan-Slavic, but they actually come from the medieval coat of arms of the Duchy of Carniola, consisting of a blue eagle on a white background with a red-and-gold crescent. The colors of the flag were considered national colours before they were first arranged on a flag during the rise of nationalism in Europe. The existing tricolour was created during the Spring of Nations in 1848, when a group of students from Ljubljana took the colours from the Carniolan coat of arms, arranging them in such a way that it resembled the Russian national flag. It was first exposed on April 7 1848 on a building in the proximity of Prešeren Square in Ljubljana. Despite opposition from the local Ethnic Germans it was subequentely recognized by the Austrian Government as the official flag of Carniola. This formal recognition was unique, since the Austrian Government otherwise tended to persecute national symbols of the single nations composing the Empire. In addition, Austrian authorities saw all tricolours as basically nationalist and potentially revolutionary symbols, so Austrian provinces (as the Empire itself) were only allowed to use bicolours (the only exception being the flag of the Kingdom of Croatia and Slavonia, since it was interpreted to be a combination of the Croatian and Slavonian bicolours). So the official recognition of the Carniolan white-blue-red tricolour instead of the traditional white-blue bicolour was seen as a major achievement by the Slovenians and it quickly became the symbol representing the idea of United Slovenia. In the second half of the 19th century, the Slovenian national tricolur became the only truly all-Slovenian symbol, representing all Slovenians, regardless of the historical region in which they lived.

The flag continued to be associated with Slovenia during the country's incorporation into Yugoslavia. In the interwar period, it was also used by the Slovenians of the Julian March that were annexed to Italy, where it was prohibited and persecuted by the fascist regime. During World War II it was used by both the Resistance Movement and the anticommunist militia. In 1945 a red star was placed on the flag, which was used by the Socialist Republic of Slovenia. Following Slovenian independence from Yugoslavia, the red star was removed and the new coat of arms, designed by Marko Pogačnik, was added. The flag was officially adopted on June 27, 1991, following a long and controversial dispute about the coat of arms of the new Republic.

The civil and state ensign for ships has the same design as the national flag, but a different shape (2:3 instead of 1:2). (Boats up to 24 meters use the national flag as an ensign.http://www.crwflags.com/fotw/flags/si~civ.html) The naval jack is a white, blue, and yellow horizontal tricolor.

In 2004, a campaign started to partially or completely alter the flag in order to enhance Slovenia's international recognition, and especially to differentiate it from Slovakia and its flag. An eleven-striped design won the official contest. Public opinion seems to be strongly against changing the flag at the moment.