Köpmangatan (Swedish: "The Merchant Street") is a street in Gamla stan, the old town of , Sweden. A parallel street to Trädgårdsgatan, it stretches from the central square to Köpmantorget, intercepted by Trädgårdstvärgränd, Skeppar Olofs Gränd, Peder Fredags Gränd, Själagårdsgatan, Staffan Sasses Gränd, Baggensgatan, and Bollhusgränd.
First mentioned in Latin in 1323 as in medio vici dicti køpmannagatu ("on the street called køpmannagatu"), the street served the merchants of Stockholm during the Middle Ages, and was the main connection between Stortorget and the fish market outside the eastern wall. One of the city's medieval gates, Köpmanporten ("The Merchant's Gate"), was once found in the eastern end of the street, until its demolition in 1685 called Köpmanvalvet ("The Merchant's Vault"), a vault stretching across the street, thus connecting the blocks south and north of it and supporting a two stories building.
Coordinates: 59°19′30.3″N 18°04′20.4″E / 59.325083°N 18.072333°E