The M-28 or M-29 Davy Crockett Weapon System was a tactical nuclear recoilless smoothbore gun for firing the M388 nuclear projectile, armed with the W54 nuclear warhead, that was deployed by the United States during the Cold War. It was the first project assigned to the United States Army Weapon Command in Rock Island, Illinois. It remains one of the smallest nuclear weapon systems ever built, with a yield of 20 tonnes of TNT (84 GJ). It is named after American folk hero, soldier, and congressman Davy Crockett.

A tactical nuclear weapon (TNW) or non-strategic nuclear weapon (NSNW) is a nuclear weapon that is designed to be used on a battlefield in military situations, mostly with friendly forces in proximity and perhaps even on contested friendly territory. Generally smaller in explosive power, they are defined in contrast to strategic nuclear weapons, which are designed mostly to be targeted at the enemy interior far away from the war front against military bases, cities, towns, arms industries, and other hardened or larger-area targets to damage the enemy's ability to wage war. As of 2024, tactical nuclear weapons have never been used.