The Solun affair (Солунска афера) was one of the largest crackdowns faced by the Internal Macedonian Revolutionary Organization (IMRO) in the early 20th century. It began in January 1901, when Ottoman authorities arrested key IMRO members in Thessaloniki (Solun), suspecting a major revolutionary conspiracy.

The affair led to widespread arrests and interrogations, severely disrupting IMRO’s operations in the Solun Vilayet. Many activists were forced into exile, primarily fleeing to Bulgaria. The crackdown also resulted in the imprisonment of nearly the entire Central Committee, allowing Ivan Garvanov to take control of IMRO.

The Ottoman Empire intensified its surveillance and military presence, suspecting that weapons and fighters were being smuggled from Bulgaria into Macedonia. This led to restrictions on travel, increased passport controls, and military reinforcements in the region.

The Solun affair significantly weakened IMRO’s underground network but also paved the way for future revolutionary actions, including the Ilinden Uprising of 1903.