A very small light tank (6 tons) with a crew of two, driver and commander, armed with two light 0.3" machine guns (with 1500 rounds), which was produced in the mid 1930s as a training tank. Over 800 tanks were produced in 1935, and the tank was used by the German forces which participated in the Spanish civil war.

When World War 2 started the German army had nearly 1500 Panzer I tanks. They participated in the Blitzkrieg invasion of Poland in 1939, although it was known that they are not suitable for front line fighting because of their lack of firepower and very thin armor. In the Blitzkrieg invasion of France in 1940 only 500 of them participated. The others remained in Germany and Poland.

By the end of 1941 they were no longer used in front line service, except a command tank version, which contained a small map table and extra radio equipment for use by Panzer unit commanders. The chassis of the obsolete tanks was converted for carrying ammunition or an anti-tank gun, but these also became obsolete and were phased out.