Derventa is a city in Republika Srpska, Bosnia and Herzegovina. It is situated in the Posavina region, northwest of the city of Doboj. As of …Derventa is a city in Republika Srpska, Bosnia and Herzegovina. It is situated in the Posavina region, northwest of the city of Doboj. As of 2013, the town has a total of 11,631 inhabitants, while the municipality has 27,404 inhabitants.