"'The bright sun was extinguish'd': The Bologna Prophecy and Byron's 'Darkness'" describes the previously-unknown historical circumstances that inspired Byron's apocalyptic poem about the death of the sun.  Byron's poem was written a month to ten days after the day (18 July 1816) on which an astronomer in Bologna had predicted that the sun would burn out and plunge the world into darkness.  1816 was the fabled "Year Without a Summer," the coldest European summer on record, during which flooding, landslides, incessant rain, and darkness across the continent intensified the misery and social unrest already caused by failing crops, postwar recession and unemployment, and governmental repression.  Along with the weather, the remarkable proliferation of sunspots at the time intensified the fears of the population of Europe.  Consequently, when the Italian astronomer predicted the death of the sun on 18 July, the story spread quickly and caused widespread apprehension, panic, suicides, and riots.  My article reconstructs the historical moment by tracing references to the prophecy through dozens of contemporary newspaper articles, letters, and diary entries, as well as examining a political satire on the subject published by William Hone.  I argue that it is highly likely that Byron and his circle at Geneva were aware of the Bologna prophecy; it was well-known in England, France, America, and Switzerland, and I demonstrate that Coleridge and the painter Joseph Farington knew of it, as well as John Cam Hobhouse and Thomas Moore, Byron's two closest friends.  I analyze Byron's poetic treatment of the death of the sun in the context of the newspaper articles' descriptions of the coming disaster as well as in the context of Byron's contempt for apocalyptic and millenarian thinking, as evidenced in his mockery of the prophetess Joanna Southcott.