Mjällby is a locality in Sölvesborg Municipality, in Blekinge County, Sweden. Mjällby lies at 11 m above sea level. It has 1,379 inhabitants (2023). The nearest city is Kristianstad, 32 km to the west. Beaches nearby: Hällevik (4.3 km), Västra Torsö (5.2 km), Sandviken (5.3 km). Among the landmarks around are Stentoften Runestone (5.7 km), St. Nicholas Church (5.7 km) and Bäckaskog Castle (21 km).