The national flag of Azerbaijan, often referred to as the Tricolor flag (), is a horizontal tricolor that features three equally sized bars of bright blue, red, and green; a white crescent; and a centred eight-pointed star. The flag has become the predominant and most recognizable symbol of Azerbaijan. The bright blue represents Azerbaijan's Turkic identity, the red represents progress, and the green represents Islam, which is Azerbaijan's majority religion.
The Azerbaijani Flag Day, held every year on 9 November, was established by Law No. 595 on 17 November 2009. The day commemorates the first official adoption of the tricolor as a national flag by the Azerbaijan Democratic Republic, which occurred on 9 November 1918. The flag was used by the republic until the 1920 Soviet invasion of Azerbaijan. It was reinstated, with slight variations to the colors and size, on 5 February 1991 following the country's independence from the Soviet Union.
The flag is referred to in the national constitution and mentioned twice in the national anthem, Azərbaycan marşı. On land, the flag is used as the civil, state and war flag; at sea, it is used as the civil, state, naval ensigns, and the naval jack. The Azerbaijani law regulates the flag's use and display, protecting it from desecration. The flag also has official status in Nakhchivan, an autonomous republic within Azerbaijan.
History
Azerbaijan Democratic Republic (1918–1920)
thumb|[[File:FIAV historical.svg|23x15px Flag of Azerbaijan between 21 June and 9 November 1918]]
thumb|150px|[[File:FIAV historical.svg|23x15px ADR flag made by Mammad Amin Rasulzade during the years of emigration]]
On 28 May 1918, the Azerbaijan Democratic Republic (ADR) declared independence. One of the first actions of the republic was the adoption of national symbols. Taking inspiration from the flag of the Ottoman Empire, the ADR adopted its first state flag on 21 June 1918, which depicted a white crescent and a white eight-pointed star on a red background. The new flag was almost identical to the old Ottoman Empire flag, which also featured an eight-pointed star until 1844 when it was replaced by a five-pointed star. The similarities between the flags reflected the hegemony of the Ottoman Empire at the time, as well as the ethnic kinship between the Turkic populations of ADR and the Ottoman Empire.
Within a few months, the newly adopted flag began to be questioned due to it exclusively representing Turkism. Thus, it was suggested that a new flag be created. The new flag was to reflect three ideas: Turkism, Islamism and the desire for progress. These ideas reflected the official ideology of ADR, which was "Turkicisation, Islamicization, and Modernisation". The formation of these ideas was influenced by the work of Islamic ideologist Jamal al-Din al-Afghani who, in his books "The Philosophy of National Unity and the True Essence of Religious Unification" and "Islamic Unity", wrote that the progress of Muslim peoples is possible under the condition of religious consolidation, national unity and the study of the progressive traditions of European statehood.
On 9 November 1918, a draft of an updated state flag was approved. The colors of the flag were borrowed from Ali bey Huseynzade's concept Turkify, Islamize, Europeanize. The new flag was a horizontal tricolor of blue, red and green with a white crescent and an eight-pointed star placed in the centre.
On 7 December 1918, the updated state flag was raised over Azerbaijan's parliament building. In a speech to the parliament, Mammad Amin Rasulzade, the Azerbaijani National Council chairman who had declared ADR's independence, stated: "[...] and for this reason, gentlemen, the National Council has raised this three-colored flag, which represents Azerbaijan, and this flag, the symbol of Turkic sovereignty, Islamic culture, and modern European power, will always fly above us. This flag, once raised, will never come down again".
Use of the Azerbaijan Democratic Republic flag after 1920
thumb|right|Patch worn by the [[Azerbaijani Legion which fought for Nazi Germany during World War II]]
After the fall of the Azerbaijan Democratic Republic in April 1920 following the Red Army invasion, their flag was used by emigrant organizations outside the Soviet Union. During World War II, the ADR flag was used by the battalions of the Azerbaijani Legion, who were military formations of ethnic Azerbaijanis fighting on the side of Nazi Germany. Depicted on the sleeve emblems of the Azerbaijan Legion's uniforms were three horizontal equal stripes of blue, red and green; a white crescent; and a five-pointed star on a red field. It was given to the National Museum of History of Azerbaijan in July 2003 and has since been kept in the museum.
In 1956, a protester named Jahid Hilaloghlu raised the ADR flag over Maiden Tower in Baku, showing his defiance of Soviet Azerbaijan. Hilaloghlu was sentenced to four years of imprisonment and his supporter Chingiz Abdullayev was institutionalized.<gallery caption="Flag of ADR in historical photographs" widths="250px" heights="180px" mode="packed">
Azerbaijan Parlament.jpg|<small>The first meeting of the Parliament of the Azerbaijan Democratic Republic, where a tricolor flag was hung. 7 December 1918.</small>
Azerbaijani delegation in Paris.jpg|<small>Azerbaijani delegation in Paris at the Claridge Hotel during the Paris Peace Conference, 1919. The tricolor flag of the ADR is visible in the background, on the chest of drawers.</small>
Army of Azerbaijan in 1918.jpg|<small>Officers and soldiers of the army of the Azerbaijan Democratic Republic against the background of the state tricolor</small>
</gallery>
Azerbaijan SSR (1920–1991)
thumb|[[File:FIAV historical.svg|23x15px Flag of Soviet Azerbaijan between 1952 and 1990. Ratio: 1:2]]
On 28 April 1920, Azerbaijan became a Soviet republic, as the Azerbaijan Soviet Socialist Republic (Soviet Azerbaijan). The state flags of the Azerbaijan Democratic Republic were banned during this period. While under Soviet rule, the Soviet Azerbaijan used eight different flags. Most of the flags only variated slightly. The adaptations were the result of the chaotic early years of the Soviet Union in the Caucasus. The first unofficial Soviet Azerbaijan flag was used during the Soviet conquest of Baku on 28 April 1920.
Soviet Azerbaijan's first official flag was adopted on 19 May 1921, in its first constitution under Article 104. The eighth and final flag of Soviet Azerbaijan was issued on 7 October 1952. The design was similar to the Soviet national flag but included a horizontal blue band on the bottom, which took up a quarter of the flag's height. The flag's definition was as follows: