Tidal inundation plays a critical role in shaping the hydrological dynamics and ecosystem services of the Sundarbans mangrove forest in the Ganges Delta. In this study, we configured and calibrated a coupled one-dimensional and two-dimensional (1D–2D) inundation model (MIKE FLOOD) for the Sundarbans in Bangladesh. Simulations were run with a 1-min time interval over a six-month period covering wet/dry season in Bangladesh. Model calibration was performed using gauged water level data, inundation maps, and Google Earth imagery. Using the calibrated model, we simulated inundation depth and frequency across the Sundarbans at different temporal scales. Results show clear spatial and seasonal variation in inundation extent, depth, and duration. Inundation is relatively low at the end of the dry season (February–March) and highest during the mid-wet season (July–August). Approximately 3,158 km2 (85.1%) of Sundarbans experiences at least one inundation in March, increasing to about 3,658 km2 (98.6%) in July. Although a large portion of the Sundarbans inundates during daily tidal cycles, the mean inundation depth remains shallow due to its flat topography. High-frequency inundation is observed in the northern part of the Sundarbans, particularly between the Passur and Sibsa rivers. About 75% of the Sundarbans inundates 50% of the time during dry season, increasing to 85% of time during wet season. The results provide valuable insights into the spatial and temporal dynamics of tidal inundation across the Sundarbans, which are essential for understanding the hydrological and ecological functioning of this unique mangrove ecosystem.