Abstract: The red strata in central Sichuan are primarily composed of Jurassic–Cretaceous sandstone and mudstone deposited in shallow lacustrine environments. These strata are characterized by short diagenetic time, nearly horizontal bedding, and poor cementation. Owing to their high clay mineral content, the rocks exhibit strong water sensitivity and are prone to disintegration and argillization upon water infiltration. As a result, near-horizontally bedded collapses and landslides are prone to occur, often leading to small-scale failures with severe consequences. To elucidate the disaster-causing mechanisms and evolutionary processes of collapse-landslides in the red-strata region of central Sichuan, and to improve the accuracy of early hazard identification and the effectiveness of engineering prevention measures, this study takes Suining City, a typical red-bed distribution area, as the research target. This research systematically investigates the genesis of the red beds, the physico-mechanical properties of the rock and soil mass, as well as the development characteristics and failure modes of collapses and landslides. A comprehensive methodology was adopted, including geological process analysis, physico-mechanical testing of rock and soil samples, and engineering geological analogy. The results indicate that since 2012, a total of 1,089 red-strata collapses and landslides have been identified in Suining City, exhibiting wide spatial distribution, numerous hazard points, and high disaster risk. The near-horizontally bedded sandstone and mudstone strata show weak resistance to weathering and pronounced differential weathering. Upon water exposure, they readily disintegrate and swell, promoting the development of joints and fissures within the rock mass. Under the combined effects of unloading weathering, rainfall infiltration, and human engineering activities, three primary failure modes are identified: (1) deep-seated creep-tension cracking, (2) thrust-type creep-slip tension cracking, and (3) shallow sliding-flow failure. The findings of this study provide a theoretical basis for understanding the formation and evolution mechanisms of collapse–landslides in red-strata regions, and offer scientific support for early identification, monitoring and warning, as well as engineering prevention and control of collapses and landslides in red-strata regions.