- Other names: Boonville monster, Boonville sloth
- Country reported: United States
The Beast of Boonville was a cryptid reported from Boonville, Indiana in the United States in 1936 and 1937.
The first report of the animal came in 1936, when fisherman Ralph Duff reported that a large hairy animal had torn his dog to shreds. Duff's wife saw the animal, which ran off when she screamed, and said that it was a "towering monster larger than a bear". Ralph Duff believed it was an ape, and set up bear traps along the river to catch it.
On 13 August the following year, Mrs. Duff again saw the animal, which she compared to a giant ape. After that date, residents of Boonville reported hearing "blood-curdling shrieks and yells". Posses began searching the river bottoms cautiously in the hope of tracking the beast to its lair. A police dog was reportedly mauled "so bad it had to be shot".
On 18 August a man entered the Boonville newspaper office and declared that the animal was a giant sloth which he and his uncle had captured during an expedition to Mexico two years previously. "He said they lost it near Evansville and never had found a trace of it since. He was uncertain if it was two-toed or three-toed, but averred that sloths came in both varieties". Other locals also claimed to have seen an empty circus truck in the area. On 19 August the hunt was abandoned. The next month, a man wrote to The Repulic suggesting the story had been made up by farmers to prevent people from picking their blackberries.
- The sisemité, an ape-like cryptid found in Mexico. One eyewitness, Thomas Gann of the British Museum, thought the animal he saw was a ground sloth.