Gmina Trzydnik Duży is a rural gmina (administrative district) in Kraśnik County, Lublin Voivodeship, in eastern Poland. Its seat is the village of Trzydnik Duży, which lies approximately 9 kilometres (6 mi) south-west of Kraśnik and 53 km (33 mi) south-west of the regional capital Lublin.
The gmina covers an area of 104.73 square kilometres (40.4 sq mi), and as of 2006 its total population is 6,947 (6,634 in 2013).