Hietalahdentori () is a square in Hietalahti in Helsinki, Finland. The area is known for its popular flea market, which is open from May to September. During World War I it was used as a Russian horse barracks. The market began in 1906, and was known for a long time for its high quality food. The other key destination on the square is the Hietalahti market hall, hosting a number of trendy restaurants.