Mestwinowo is a settlement in the administrative district of Gmina Liniewo, within Kościerzyna County, Pomeranian Voivodeship, in northern Poland. It lies approximately 7 km south-east of Liniewo, 23 km east of Kościerzyna, and 42 km south-west of the regional capital Gdańsk. It is located within the historic region of Pomerania. During the German occupation of Poland (World War II), in October 1939, the SS and Selbstschutz murdered 46 Polish farmers from Jaroszewy in the village, after they were previously deceitfully gathered for a formal meeting in their home village.