Osiecko [ɔˈɕɛt͡skɔ] is a village in the administrative district of Gmina Bledzew, within Międzyrzecz County, Lubusz Voivodeship, in western Poland.

The settlement was first mentioned as Magnum Oszec in a 1312 deed, when the area around Bledzew was temporarily under the rule of the Ascanian margraves of Brandenburg in the west.

From about 1320 until the Partitions of Poland in the late 18th century, Osiecko belonged to the Greater Polish Poznań Voivodeship.

After World War I, Oscht with the Posen-West Prussia frontier region remained with the German Weimar Republic according to the Treaty of Versailles.

Osiecko returned to the Republic of Poland after World War II as stipulated by the Allied Potsdam Agreement and the German population was expelled.