The Tallboy was an earth quake bomb developed by Barnes Wallis and brought into operation by the British in 1944. It weighed five tons and, carried by the Avro Lancaster bomber, was effective against hardened structures against which earlier, smaller bombs had proven ineffective.

The British aeronautical engineer Barnes Wallis presented his ideas for a 10 ton bomb in his 1941 paper A Note on a Method of Attacking the Axis Powers, which showed that a very large bomb exploding deep underground next to a target would transmit the shock into the foundations of the target, particularly since shock waves are transmitted through the ground more strongly than through air. Barnes Wallis designed the "Victory Bomber" of 50 tons which would fly at 320 mph (510 km/h) at 45,000 feet (14,000 m) to carry the heavy bomb over 4,000 miles (6,400 km), but the Air Ministry were against a single-bomb bomber and the idea was not pursued beyond 1942. Following Wallis's 1942 paper Spherical Bomb — Surface Torpedo and the design of the "bouncing bomb" for the Dam Busters of Operation Chastise, the actual design and production of Tallboy was done without a contract on the initiative of a single official within the Ministry. As such the RAF were using bombs they had not bought and which were actually still the property of the manufacturers; Vickers. This situation was regularized once their capabilities were recognised.

Amongst many accomplishments by the Tallboy, the 24 June 1944 Operation Crossbow attack on La Coupole (along with Grand Slam bombing) undermined the foundations. A Tallboy of the 8-9 June 1944 Saumur tunnel attack passed straight through the hill and exploded inside the tunnel 60 feet (18 m) below the surface.[2] The last Kriegsmarine Bismarck-class battleship, the Tirpitz, was sunk by an air attack using Tallboys.