Mykolaiv is a city and a hromada (municipality) in southern Ukraine. Mykolaiv is the administrative center of Mykolaiv Raion (district) and Mykolaiv Oblast (province). The city of Mykolaiv, which provides Ukraine with access to the Black Sea, is the location of the most downriver bridge crossing of the Southern Bug river. This city is one of the main shipbuilding centers of the Black Sea. Aside from three shipyards within the city, there are a number of research centers specializing in shipbuilding such as the State Research and Design Shipbuilding Center, Zoria-Mashproekt and others. As of 2022, the city has a population of 470,011. Mykolaiv holds the honorary title Hero City of Ukraine.

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.