Kalashnikov, who was in his 20s when he created the AK-47 just after World War II, died in his home city of Izhevsk near the Ural Mountains, where his gun is still made, a spokesman for the Udmurtia province's president said on state television.
The spokesman did not give the cause of death. Kalashnikov was fitted with a electric heartbeat stimulator at a Moscow hospital in June and had been in hospital in Izhevsk since Nov. 17, state media reported.
The AK-47, which rarely jams even in adverse conditions, went into service in the Soviet armed forces in 1949. Today, Kalashnikov rifles are still a mainstay of Russia's armed forces and police.
Known as the weapon of choice for guerrillas, the gun and its imitations have been used in conflicts around the world for decades.
At a lavish Kremlin ceremony on Kalashnikov's 90th birthday, then-President Dmitry Medvedev bestowed on him the highest state honour - the Hero of Russia gold star medal - and lauded him for creating "the national brand every Russian is proud of".
Kalashnikov, a son of Siberian peasants who never finished school, said pride in his iconic invention was mixed with the pain of seeing it used by criminals and child soldiers.