Lönnström Group was a conglomeration of metal industry companies operating in the Kaivopuisto area near Kappelinsalmi in Rauma. The first company in the group was founded in Helsinki in 1929, but it moved to Rauma in the course of 1936–1942. The group comprised five companies, the largest of them Oy Sytytin and Oy Ammus.
During World War II, Oy Sytytin and Oy Ammus made artillery munitions, such as fuses and shells, for the Finnish Defence Forces. After the war, the Lönnström companies manufactured a wide range of metal industry products, the most important being water taps, industrial chains and conveyor systems.
As early as the 1930s, Rafael Lönnström began making products for the civilian market. In the 1930s, the Lönnström Group included Rafu Lönnström Oy, which manufactured electric armatures and water taps, and Oy Partaterä, which manufactured razors.