The Ilinden–Preobrazhenie Uprising (Bulgarian: Илинденско-Преображенско въстание, romanized: Ilindensko-Preobrazhensko vastanie), consisting of the Ilinden Uprising (Macedonian: Илинденско востание, romanized: Ilindensko vostanie; Greek: Εξέγερση του Ίλιντεν, romanized: Exégersi tou Ílinden) and Preobrazhenie Uprising, was an organized revolt against the Ottoman Empire, which was prepared and carried out by the Internal Macedonian-Adrianople Revolutionary Organization, with the support of the Supreme Macedonian-Adrianople Committee, which included mostly Bulgarian military personnel. The name of the uprising refers to Ilinden, a name for Elijah's day, and to Preobrazhenie which means Feast of the Transfiguration. The revolt lasted from the beginning of August to the end of October.
The uprisings had as an aim the autonomy for Macedonia and Adrianople regions. The Ilinden Uprising in the region of Macedonia affected the Manastir vilayet, where it was organized by Macedonian Bulgarians, joined mainly by some Patriarchist Macedonian Slavs (called Grecomans and Serbomans), and some Patriarchist and Exarchist Aromanians and Albanians. A provisional government was established in the town of Kruševo, proclaimed as the Kruševo Republic. The republic was overrun after ten days by the Ottoman forces. On August 19, the closely related Preobrazhenie Uprising, organized by Thracian Bulgarian revolutionaries in the Adrianople vilayet, led to the liberation of a large area in the Strandzha Mountains, and the creation of a provisional government in Vassiliko, the Strandzha Republic. This lasted 26 days before being put down by the Ottomans. The insurrection also affected the vilayet of Kosovo and the Salonica vilayet.