[3] Historically, at various times, the territory was ruled either entirely or partly by Scythia, ancient Greeks, Old Great Bulgaria, Khazars, Kipchaks, the Mongol Empire, Lithuania, the Crimean Khanate, the Ottoman Empire, Poland, and Russia.

In the late 17th and 18th centuries the tripoint of three early modern great powers, the Polish–Lithuanian Commonwealth, the Ottoman Empire and Russia, was located at the site of the current second-largest city of Mykolaiv Oblast, Pervomaisk, a city formed by the merger of the former Polish town of Bohopol, Russian town of Olviopol and Ottoman village of Holta.

A Ukrainian military official announced a Russian withdrawal from Mykolaiv Oblast on 10 November 2022.

[8] On 4–5 July 2022 during an international Ukraine Recovery Conference (URC 2022) in Lugano, Switzerland pledged to support the rebuilding of Mykolaiv region.

[10] Among major valuable deposits and minerals there are nickel, uranium ores, granite, gneiss, quartzites.

[10] The climate is moderately continental with a mild winter of small snow amount and hot arid summer.

[10] Among main rivers there are the Southern Bug (Boh) which splits the oblast into eastern and western parts, Inhulets, and Berezan.

[3] The oblast's population density is one of the lowest in Ukraine – 45 inhabitants per square kilometre (120/sq mi).

[15][16] These are: Before July 2020, Mykolaiv Oblast was subdivided into 24 regions: 19 raions (administrative districts) and 5 city municipalities (mis'krada or misto), officially known as territories governed by city councils[17] which are directly subordinate to the oblast government.

During the 1991 referendum, 89.45% of votes in Mykolaiv Oblast were in favor of the Declaration of Independence of Ukraine.