Gmina Grunwald is a rural gmina (administrative district) in Ostróda County, Warmian-Masurian Voivodeship, in northern Poland. Gmina Grunwald is divided into 19 sołectwos. The villages with the largest population are Gierzwałd, which dates back to the 14th century, and Zybułtowo. Gierzwałd is the administrative seat of the gmina. Unusually the gmina is not named after the seat, but takes its name from the smaller village of Grunwald, because of the historical importance of the Battle of Grunwald of 1410.