An assault gun (from German: Sturmgeschütz, lit. 'storm gun', meaning "attack gun") is a type of armored infantry support vehicle and self-propelled artillery, mounting an infantry support gun on a protected self-propelled chassis, intended for providing infantry with heavy direct fire support during engagement, especially against other infantry or fortified positions, secondarily also giving some armored protection and anti-armor capability.
Assault guns were pioneered by the Soviet Union and Nazi Germany during the 1930s, initially being self-propelled guns with direct fire in mind (such as the Soviet SU-5-1), with Germany introducing the first purpose-built (and purpose-named) assault gun, the Sturmgeschütz III, in 1940.