Niseko is located on the northernmost island of Japan, Hokkaido. It is around 110 km from New Chitose Airport and 95 kms from Sapporo, Japan's 5th largest city. Niseko is approximately 800 kms north of Tokyo, the capital of Japan. You can find it on Google Maps here.
The name 'Niseko' usually refers to the ski resorts positioned on Mt. Niseko-Annupuri and the surrounding areas. Technically though, two of the four major resorts (Grand Hirafu and Hanazono) are located within Kutchan Town and two (Niseko Village and Annupuri) within Niseko Town.