Nizhneudinsky District () is an administrative district, one of the thirty-three in Irkutsk Oblast, Russia. Municipally, it is incorporated as Nizhneudinsky Municipal District. The area of the district is . Its administrative center is the town of Nizhneudinsk. Population: 31,122 (2002 Census);
Within the framework of administrative divisions, Nizhneudinsky District is one of the thirty-three in the oblast. The town of Nizhneudinsk serves as its administrative center. As a municipal division, the district is incorporated as Nizhneudinsky Municipal District.
The territory of Tofalariya is a small historical and cultural region located in the southwestern part of Nizhneudinsky District.