Mark Twain [Samuel Langhorne Clemens] (1835–1910), U.S. author. Originally a response to a newspaper reporter's inquiry about a rumor that Twain was either dead or on his deathbed in London, 1896. Mark Twain's Notebook (1935).
This line has been quoted in various ways, more powerfully, I think, as "The report of my death has been greatly exaggerated." Since it was quoted by the newspapers, it is difficult to know what Twain's exact phrasing was when he invented the line.