The Bulgarian Horror were atrocities committed by the forces of the Ottoman Empire in subduing the Bulgarian rebellion of 1876; the name was given currency by the British statesman W.E. Gladstone. Publicity given to the atrocities, especially in Gladstone's pamphlet “The Bulgarian Horrors and the Question of the East” (1876), served to arouse public sympathy in Europe for the Bulgarians and other southern Slavs attempting to gain independence from the Ottoman Empire.

The Bulgarian revolt was part of the eastern crisis of 1875–78. This, in turn, was one of many crises that marked the so-called Eastern Question, the problem of the power vacuum created by the decay of the Ottoman Empire, that occupied European governments through much of the 19th century.

After decades of nationalistic ferment, an uprising broke out in Bosnia and Herzegovina in 1875 and spread to Bulgaria the following spring. It was cruelly suppressed by the Turks, especially the poorly disciplined irregulars known as bashi-bazouks. About 15,000 persons were said to have been massacred at Philippopoli (now Plovdiv), and many villages and some monasteries were destroyed. Isolated risings in the mountains were crushed with equal severity.

Gladstone, then in opposition and contemplating retirement from the leadership of the Liberal Party, was moved by reports of the atrocities to write his pamphlet and to campaign vigorously against the foreign policy of the Conservative prime minister, Benjamin Disraeli, which favoured supporting the Ottoman Empire as a counterweight to Russia.

Despite widespread public indignation, the European powers did little to alleviate the situation, and the climate of opinion changed after Russia attacked Turkey in 1877. The crisis ended with the Congress of Berlin (see Berlin, Congress of) in 1878, which created a small, autonomous principality of Bulgaria, still under the sovereignty of the Ottoman Empire and confined to territory north of the Balkan Mountains.