Mykolaiv Oblast is an oblast (province) of Ukraine. The administrative center of the oblast is the city of Mykolayiv. The Mykolaiv Oblast is located in the southern half of Ukraine. Its area (24,600 km²), comprises about 4.07% of the total area of Ukraine.

The Mykolaiv Oblast borders upon the Odesa Oblast in the west-southwest, the Kirovohrad Oblast in the north, the Dnipropetrovsk Oblast in the northeast, and the Kherson Oblast on the southeast.

On the south the obalst' is also bordered by the Black Sea. On the shoreline, there are several ports and the Mykolaiv International Airport.