The subject of this research is the policy of government supervision of the commercial and industrial spheres of the Russian Empire in the 19th century. The object of the study is the activities of the gendarmerie corps officials that carried out that supervision. These activities of the gendarmerie are studied on the example of the supervision of fairs in Siberia, which had their own special aspects. This function of the Russian gendarmerie has been studied fragmentarily in Russian historiography. To disclose the subject and object of the research, the following tasks were set: 1) to establish the reasons for the attention of the gendarmerie to fairs taking place in Siberia; 2) to identify those fairs that required a mandatory gendarme presence; 3) to establish the functions performed by the gendarmerie officials during their occupation of the post of temporary commandant at fairs; 4) to determine the reasons for disestablishing the gendarme supervision of the fairs. The sources for writing the article were: materials from the gendarmerie and executive branch funds of the central Russian archives (State Archive of the Russian Federation, Russian State Historical Archive), legislative acts of the imperial government, as well as the gendarmerie corps orders. Many used archival materials were introduced into scientific circulation for the first time. In the process of the research the author came to the following conclusions. Since 1833 the officials of the gendarmerie corps were appointed to the temporary commandants of the fairs, during which they received great powers and duties. The activities of the gendarmes in this position were regulated by instruction specially written for them. They also used the traditional gendarme surveillance tool in the form of reports that were compiled at the end of the fairs and were sent to the gendarmerie authorities. The gendarme officers not only monitored public order, but also monitored the course of bidding, being intermediaries in the event of trade-related conflicts. The choice of fairs to be visited by the gendarmes was largely determined by the trade turnover of these fairs, by the availability of fairs to be visited by the gendarmes, and by the needs to comply with state interests. The latter circumstance gives reason to assert that gendarme supervision was an actively used tool in government policy to control the commercial and industrial spheres. The gendarme officials themselves tried not to formally fulfill the duties of temporary commandant, but as the documents show, tried to improve trading activities, noting the possible benefits for the local population.