Trzciniec Duży [ˈtʂt͡ɕiɲɛt͡s ˈduʐɨ] is a village in the administrative district of Gmina Kosów Lacki, within Sokołów County, Masovian Voivodeship, in east-central Poland. It lies approximately 4 kilometres (2 mi) south of Kosów Lacki, 20 km (12 mi) north-west of Sokołów Podlaski, and 87 km (54 mi) north-east of Warsaw.