Ust-Ishimsky District () is an administrative and municipal district (raion), one of the thirty-two in Omsk Oblast, Russia. It is located in the northwest of the oblast. The area of the district is .} Its administrative center is the rural locality (a selo) of Ust-Ishim, which, as its name indicates, is located at the confluence of the Ishim River with the Irtysh.
Population: 13,480 (2010 Census); The population of Ust-Ishim accounts for 35.6% of the district's total population.
The Ust'-Ishim man, an ancient skeleton dated to 45,000 years before present, was discovered on the bank of the Irtysh River in Ust-Ishimsky District.
Russians 70.6%, Tatars 25.3%, Ukrainians 1.2%, Germans 1.1%, Chuvash 0.6%.