Abstract <p>The present paper deals with the Quaternary history of Lake Baikal and adjacent areas, emphasizing issues related to water level fluctuations and Lake Baikal outflows. The fluctuations in lake level are documented through a series of terraces, situated within the continental region and on Bolshoi Ushkanii Island, which are positioned at elevations reaching up to 215 m above the contemporary lake level. The lake’s substantial fluctuations in water level are attributed to tectonic and climatic factors. The formation of Lake Baikal, spanning a duration of 25 million years, is well-documented, while the geological data on the lake outflow channels is more recently documented, extending only 3 million years back. The current knowledge on the outflow channels indicates the presence of three channels, all situated within the South Baikal Basin. The most ancient of these is the Goloustnaya-Manzurka Valley, characterized by the presence of alluvial gravel and sand (“Manzurka alluvium”) that extends from Lake Baikal to the Lena River valley. The second outflow channel is situated at the southwestern extremity of Lake Baikal. The final contemporary outflow channel is the Listvenichny Bay area, where the Angara River originates. A thorough analysis of the geological and geomorphological data reveals that the outflow’s evolution was significantly impacted by catastrophic events, leading to a rapid decline in the water level of Lake Baikal by tens or hundreds of meters over a brief period. The collapse and slide of some coastal ridges into the lake’s water body has been identified as a primary cause outburst floods. Evidence of catastrophic floods is evident in the Angara River valley and its tributary valleys, as well as in the system of present-day valleys that are confined to the ancient Goloustnaya-Manzurka Valley. Preliminary findings, based on an analysis of integrated geological and geophysical data, indicate that the period of formation of the Manzurka outburst flood is estimated to have occurred approximately 800 to 1000&#xa0;thousand years ago. The evolution of the Angara outflow channel was triggered by two major catastrophic events: MIS 5e and ~12 ka, respectively. These events are associated with the partial collapse of the Primorsky Ridge and the formation of an outburst flood along the Angara River. The present paper proposes a catastrophic model for outflow channel formation in Lake Baikal, which resolves numerous issues concerning the Quaternary geology and geomorphology of this region.</p>