T34 Calliope rocket launcher mounted on an M4 Sherman tank in action in 1945

The Rocket Launcher T34 (Calliope) was a tank-mounted multiple rocket launcher used by the United States Army during World War II. The launcher was placed atop the M4 Sherman, with its prominent vertical side frames anchored to the turret's sides and fired a barrage of 4.5-inch (114 mm) M8 rockets from 60 launch tubes. It was developed in 1943; small numbers were produced and were used by various US armor units in 1944–45. Its name comes from the calliope, a musical instrument also known as a steam organ, which has similar parallel or clustered pipes.

The T34 version of the Calliope carried 60 rockets arranged in a group of 36 permanent tubes on the top, and a pair of jettisonable groups of 12 tubes (24 tubes in total) on the bottom. Each rocket was a 4.5-inch (110 mm) fin-stabilized projectile with the same explosive yield as a M101 howitzer and had a maximum range of 4,100 yards (3,700 m).

The rack was physically connected to the barrel of the 75 mm gun M2–M6 using an arm. This arm was connected to the rack via a pivoting joint and clamped to the gun with a split ring. This allowed the missile launcher to follow the same elevation and depression arc of +25 to -12 degrees. A large support beam bolted to the left and right turret cheeks supported the weapon placed one meter above the turret.

The rockets were fired electrically using cables that were inserted through the tank commander's hatch. The main gun could not be fired once the rocket launcher had been attached. This caused the tank crews to modify the launcher installation in the field, thereby allowing the main gun to fire, albeit at a reduced elevation for the launcher. Later models of the launcher also had flame deflectors to help prevent rocket exhaust from entering the engine compartment.