The Kolašin Affair (Serbian: Колашинска афера) was a rebellion in the Montenegrin military against the dictatorship of the Prince of Montenegro, Nikola I Petrović-Njegoš, that broke out in 1909.
It followed the failed Bombaš Affair (Бомбашка афера), a conspiracy organized in 1907 by a group of Montenegrin students connected to the Black Hand to break the Montenegrin government through terrorist attacks (with bombs, hence "Bombaši"), and ultimately unite Montenegro with Serbia, that was detected and led to numerous arrests in 1908.
In the same year, a secret organization of Montenegrin politicians and political emigrees in Belgrade in opposition to Nikola I was formed.
The organization had important subsidiaries in Vasojevići, Kuči and Bratonožići, and allegedly had 1,000 members.
It was detected by the Montenegrin police and led to the imprisonment and death sentences of the conspirators.