Mykolaiv Raion is a raion (district) in Mykolaiv Oblast, Ukraine with a pre-war population of 636,832.. Its administrative center is the city of Mykolaiv.

Mykolaiv Oblast, also referred to as Mykolaivshchyna, is an oblast (province) of Ukraine. The administrative center of the oblast is the city of Mykolaiv. At the most recent estimate, the population of the oblast stood at 1,091,821.