Posavina Canton lies on the river Sava (after which it is named) thatforms a natural border between Bosnia and Herzegovina and Croatia. Posavina as a region includes other parts of Bosnia and Herzegovina and parts of Croatia, so the canton is sometimes called Bosnian Posavina (Bosnian Posavina). It is mainly agricultural area characterized by flat lowland and lack of mountains. The center of the canton is Orašje.
2013 census shows that 48,089 people are living in the Canton.
Thanks to its favourable geographical position and surrounding mountains, Bosnian Posavina has a moderate continental climate. In July, which is the warmest month, average temperature is around 21°C. Winters are temperate and cold, and the average temperature in January is 2°C. Rainfall is harmoniously distributed throughout the year with May and June being the months with most rain.