A fire balloon (風船爆弾, fūsen bakudan?, lit. "balloon bomb"), or Fu-Go, was a weapon launched by Japan during World War II. A hydrogen balloon with a load varying from a 12-kilogram (26 lb) incendiary to one 15 kg (33 lb) antipersonnel bomb and four 5 kg (11 lb) incendiary devices attached, they were designed as a cheap weapon intended to make use of the jet stream over the Pacific Ocean and wreak havoc on Canadian and American cities, forests, and farmland.
The balloons were relatively ineffective as weapons but were used in one of the few attacks on North America during World War II.
Between November 1944 and April 1945, Japan launched over 9,300 fire balloons. About 300 balloon bombs were found or observed in North America, killing six people and causing a small amount of damage.