Nikolayevsky District (Russian: Никола́евский райо́н) is an administrative[1] and municipal[4] district (raion), one of the twenty-one in Ulyanovsk Oblast, Russia.

It is located in the southwest of the oblast.

The area of the district is 2,084.27 square kilometers (804.74 sq mi).

[citation needed] Its administrative center is the urban locality (a work settlement) of Nikolayevka.

[7] The population of Nikolayevka accounts for 23.5% of the district's total population.