Abstract: To explore the spatiotemporal evolution of the bottomland in Dongting Lake since the middle stage of the Republic of China, this study examined the historical topographic maps and aerospace remote sensing data concerning the study area for over 10 time periods since the 1930s. Based on remote sensing image interpretation, statistical data analysis, and historical comparison, this study analyzed the temporal variations in the bottomland area of Dongting Lake in various periods to infer the corresponding spatial distributions of the bottomland. The results show that the spatial development of the bottomland in Dongting Lake was primarily characterized by the rapidly advancing delta at the mouth of the east branch of the Ouchi River and Piaowei Islet in East Dongting Lake, the alluvial deposits along the Caowei and Songzhu rivers in the north of South Dongting Lake, and the “Jiangnan Grassland” landscape formed by the bottom uplift of Qili and Muping lakes. The bottomland area in Dongting Lake expanded from 1 622.17 km² in 1 938 to 1 962.28 km² in 2018, coupled with the 980.96 km² of reclaimed high bottomland, suggesting a net increase of 1 321.07 km². In terms of spatial distribution, the bottomland area exhibited an undulating trend rather than a continuous increase. It manifested a significant expansion from 1938 to 1948 and 1958 to 1998 but a slow shrinkage from 1948 to 1958 and 1998 to 2018. Overall, the results of this study provide objective data for preserving lakeshore ecosystems and biodiversity and serving ecological restoration and environmental conservation in the Yangtze River basin.