Osiek [ˈɔɕɛk] ⓘ is a town in Staszów County, Świętokrzyskie Voivodeship, Poland, with 2,001 inhabitants (2010). The town lies in Lesser Poland, along the National Road nr. 79, which goes from Warsaw to Bytom. Osiek is located 15 kilometers northeast of Połaniec, and 18 kilometers west of Tarnobrzeg, 180 meters above sea level.
Its main point of interest is St. Stanisław parish church, built in the late 17th century. Osiek has a rail station called Osiek Staszowski, on a secondary importance line which joins Tarnobrzeg with Włoszczowice.