Södertälje (södərtĕlˈyə) [key], city (1990 pop. 58,198), Stockholm co., E Sweden, on a narrow bay of Lake Mälaren, near Stockholm. It is an industrial center and a health resort. Manufactures include motor vehicles, machinery, tobacco products, and pharmaceuticals. Originally known as Tälje, it was a trade center during the Viking era (9th–11th cent.) and is one of Sweden's earliest cities. The Södertälje Canal, connecting Lake Mälaren and the Baltic Sea, was built in 1807–19 and was enlarged to accommodate bigger ships in 1917–24.