Howard Phillips Lovecraft (August 20, 1890 – March 15, 1937) was an American author of horror, fantasy, and science fiction, especially the subgenre known as weird fiction.

Lovecraft's guiding literary principle was what he termed "cosmicism" or "cosmic horror", the idea that life is incomprehensible to human minds and that the universe is fundamentally alien. Those who genuinely reason, like his protagonists, gamble with sanity. As early as the 1940s, Lovecraft had developed a cult following for his Cthulhu Mythos, a series of loosely interconnected fiction featuring a pantheon of human-nullifying entities, as well as the Necronomicon, a fictional grimoire of magical rites and forbidden lore. His works were deeply pessimistic and cynical, challenging the values of the Enlightenment, Romanticism, and Christian humanism. Lovecraft's protagonists usually achieve the mirror-opposite of traditional gnosis and mysticism by momentarily glimpsing the horror of ultimate reality and the abyss.

Although Lovecraft's readership was limited during his life, his reputation has grown over the decades, and he is now regarded as one of the most influential horror writers of the 20th century. According to Joyce Carol Oates, Lovecraft — as with Edgar Allan Poe in the 19th century — has exerted "an incalculable influence on succeeding generations of writers of horror fiction". Stephen King called Lovecraft "the twentieth century's greatest practitioner of the classic horror tale."