Mariinsko-Posadsky District (Russian: Марии́нско-Поса́дский район; Chuvash: Сĕнтĕрвăрри районӗ, Sĕntĕrvărri rayonĕ) is an administrative[1] and municipal[4] district (raion), one of the twenty-one in the Chuvash Republic, Russia.

It is located in the northeast of the republic.

The area of the district is 686.1 square kilometers (264.9 sq mi).

[2] Its administrative center is the town of Mariinsky Posad.

[7] The population of Mariinsky Posad accounts for 38.0% of the district's total population.