The town and district of Osieczna are situated in south-western Poland, 9 km to the north-east of Leszno, on the road from Leszno to Śrem. In 1999, as a result of the administrative reform the town and the district returned to the Province of Wielkopolska (before the previous reform in 1975, it was the Province of Poznań). The old Province of Leszno was liquidated, and Osieczna is now situated in Leszno County in the mentioned Province.
The town, which has a population of about 2,000, lies at the southern end of the Krzywiń Lake District, which is a fragment of a bigger geographical region, namely the Leszno Lake District. On the east, the town borders the shores of Lake Łoniewskie. This location by a lake and in a hilly area of a bottom moraine makes Osieczna one of the most picturesque places of the Leszno Region and Wielkopolska.
The town has a diversified lay of the land. The Market Square and the Church are the highest points of the town with all streets which lead to them rising upwards. The Market Square and the church are situated at a height of 100 m above sea level whereas the not flooded parts of the valley of the lake reach a height of a little above 70 m.
The lake was formed tens of thousands of years ago, during the last, so called Baltic glaciation in the area of present Poland. This was during the farthest southern expansion of this glaciation - the so called Leszno stade. The lake was formed in the marginal zone of the glaciation, at the end of the glacier. It occupies a fragment of an extensive gully, which stretches from Wonieść to Osieczna, Grodzisko and Górzno. There are 11 lakes in the valley. In the past, when the water level was 2 metres higher, the present lakes made one huge water reservoir, which the most famous Polish historian, Jan Długosz, called "Woniesko".
The area around Osieczna has a relatively young postglacial sculpture of the earth's surface. To the south of the town, there are relics of the Leszno end moraine. It has modest dimensions as the ice cover was very thick, and the stagnation of the front of the glacier did not last long. The moraine was washed out by the flooding waters to a large extent and therefore it forms now only single hills, so called island mountains. One of them - Góra Jadwigi - has a height of 150 m above sea level and is the highest elevation in the area around Leszno and Osieczna.
The beauty of landscape is also characteristic of the area around Stanisławówka. This is the place of the so called Wydor or Widor¸ which is a deep erosion cut with a narrow streamlet running towards the lake. This place full of charm and shrouded in mystery owes its unusual character not only to the configuration of the area but also many rare species of plants and imposing trees.
Osieczna is abundant in such places. In addition to the above place, which is quite exceptional in its beauty, the town is surrounded with fields, meadows, marshy grounds and forests.
From the south, the lake valley borders a compact forest area around Łoniewo and Kąkolewo. The forest consists mainly of deciduous trees: beeches, sycamores, oaks and ashes. A large forest area (Osieczna Forest) with mainly coniferous trees stretches on both sides of the road which connects Osieczna and Leszno. There are also little wooded areas in the area of Drzeczkowo and Goniembice, and farmland stretches as far as the eye can reach to the west and east of Osieczna.