The North Sikkim Glacial Lake Inventory (NSGLI-2025) is a geospatial dataset containing polygon boundaries and associated attributes. A total of 467 glacial lakes were identified and mapped across the Sikkim Himalaya, India, of which 465 were retained after topographic edge-matching. Lake boundaries were manually delineated from high-resolution satellite imagery and integrated with glacier outlines and digital elevation model data. The dataset includes lake identifiers, geographic coordinates, surface area, perimeter, elevation statistics, glacier proximity metrics, and geomorphological classifications. Moraine-dammed, glacial erosion, ice-dammed, and other glacial lake types are included. Quality assessment was performed through comparison with previous regional inventories and uncertainty evaluation of mapped lake areas. The dataset is intended to support studies of glacier retreat, glacial lake evolution, cryosphere change, hydrology, and glacial lake outburst flood hazards in High Mountain Asia.