Ostroh is a city located in the Rivne Oblast of western Ukraine. It is situated along the banks of the Horyn River and serves as the center of the Ostroh urban hromada.
The city has a population of 14,894. Historically, it served as the administrative center of the Ostroh Raion until 2020; however, as a city of oblast significance, it did not belong to that raion during that period.