The Ilinden–Preobrazhenie Uprising or simply the Ilinden Uprising of August 1903 (Bulgarian: Илинденско-Преображенско въстание, Ilindensko-Preobrazhensko vastanie, (Macedonian: Илинденско востание, Ilindensko vostanie) was an organized revolt against the Ottoman Empire, which was prepared and carried out by the Secret Macedonian-Adrianople Revolutionary Organization.^[1] The British researcher of the Balkans H. N. Brailsford wrote in his book Macedonia: Its Races and Their Future: "The moment for which the Bulgarian population had been preparing for ten years arrived on the festival of the Prophet Elijah's day — the evening of Sunday, August the 2nd, 1903." ^[2] At the same time on the other end of the SMARO's territory, in Eastern Thrace, the leaders of the Adrianople Vilayet comitajis, had unanimously agreed that they were not ready for uprising, but of a feeling of solidarity, had voted for a rising. So in Strandzha the rising had begun on the Feast of the Transfiguration, August 19, 1903.^[3]

The rebellion in Macedonia affected most of the central and southwestern parts of the Monastir Vilayet receiving the support mainly of the local Bulgarian peasants and to some extent of the Aromanian population of the region. Provisional government was established in the town of Kruševo (to the west of Prilep), where the insurgents proclaimed the Kruševo Republic under the presidency of the school teacher Nikola Karev, which was overrun after just ten days, on August 12.^[4] On August 19, a closely related uprising organized by Bulgarian peasants in the Adrianople Vilayet led to the liberation of a large area in the Strandzha Mountains near the Black Sea coast, and the creation of a provisional government in Vassiliko, the Strandzha Republic. This lasted about twenty days before being put down by the Turks.^[4]