International Solidarity Day of Azerbaijanis is observed worldwide every December 31. This public holiday was first declared in 1991 by Heydar Aliyev, who later became the President of Azerbaijan. The day commemorates significant events from December 31, 1989, when the nationalist organization Popular Front of Azerbaijan advocated for the removal of borders between the Azerbaijan Soviet Socialist Republic and Iran, leading thousands of Azerbaijanis to cross the Aras River to reunite with their compatriots in Iranian Azerbaijan. Additionally, the first World Congress of Azerbaijanis took place in Istanbul, Turkey, on the same day. The holiday is celebrated not only in Azerbaijan but also by the Azerbaijani diaspora, which includes large communities in countries such as Russia, Turkey, Georgia, Kazakhstan, Germany, Ukraine, the Netherlands, Kyrgyzstan, the United Kingdom, and the United States. On this day, Azerbaijani expatriates honor their language, culture, and historical heritage.