Gmina Sejny, is a rural gmina (administrative district) in Sejny County, Podlaskie Voivodeship, in north-eastern Poland, on the Lithuanian border.

The gmina covers an area of 218.01 square kilometres (84.2 sq mi).

As of 2011 its total population was 4,156 and 15.5% of the inhabitants were Lithuanians.

[1] Gmina Sejny contains the villages and settlements of Babańce, Berżałowce, Berżałowce-Gajówka, Berżniki, Berżniki-Folwark, Bose, Bubele, Burbiszki, Degucie, Dubowo, Dusznica, Dworczysko, Gawieniańce, Grudziewszczyzna, Gryszkańce, Hołny Majera, Hołny Wolmera, Jenorajście, Jodeliszki, Kielczany, Klejwy, Klejwy PGR, Kolonia, Kolonia Sejny, Konstantynówka, Krasnogruda, Krasnowo, Krejwińce, Lasanka, Łumbie, Markiszki, Marynowo, Marynowo-Kolonia, Nowosady, Nożegary, Ogrodniki, Olszanka, Poćkuny, Podlaski, Półkoty, Posejanka, Posejny, Rachelany, Radziucie, Radziuszki, Rynkojeziory, Sumowo, Świackie, Sztabinki, Wigrańce, Wigrańce-Leśniczówka, Zaleskie, Zaruby and Żegary.

Gmina Sejny is bordered by the town of Sejny and by the gminas of Giby, Krasnopol and Puńsk.