<p>This study attempts to define the mountain heatwave across the Indian Himalayas for the gridded datasets by adapting the definition from the India Meteorological Department. The heatwaves are estimated using ERA5 reanalysis data from 1961 to 2024 with an aim to examine their intensity, frequency, duration and elevation dependency, and further to identify the heatwave hotspots across the Himalayas. The findings indicate a significant rise in maximum temperature, particularly in the higher reaches of the northern part, increasing the heat stress. Although the number of heatwave days and spells is declining in some regions, the overall strength and intensity of heatwaves have increased in recent periods. The heatwave-affected grid points follow a declining gradient of elevation from the western Himalayas to the eastern Himalayas. The contribution of the central Himalayas is highest in the occurrence of heatwaves in lower elevations, while the western Himalayas dominates the higher elevations. The duration of heatwaves is declining at higher elevations. The heatwaves are intensifying at higher elevations across the Himalayas, with the western Himalayas experiencing the strongest. These intensifications are driven by elevation-dependent warming through snow-albedo and cloud-radiation feedbacks, an increase in atmospheric water vapour, nocturnal clouds and absorbing aerosols. The 1500–1750&#xa0;m and 750–1000&#xa0;m elevation bands emerge as primary hotspots of mountain heatwaves in the Himalayas. The study advocates the need for targeted adaptation strategies and early warning systems in the Indian Himalayas.</p>