Eskilstuna's history dates back to medieval times when English monk Saint Eskil made "Tuna" his base and diocese of the South coast of Lake Mälaren. Saint Eskil was stoned to death by the pagan vikings of neighbouring town Strängnäs, and was buried in his monastery church in Tuna. Later "Eskil" was added in to the word "Tuna". Later Eskilstuna became the center for iron forges making small arms and artillery.

The city grew enormously during the Industrial Revolution and became one of the most important industrial cities of Sweden, earning the nickname "Stålstaden" ("The City of Steel"). Aside from firearms, the city also produced cutlery, scissors, keys, machine tools and precision instruments.