The Nagano-sen is a privately owned train line which runs between Nagano Station and Yudanaka Station in Yamanouchi Town, Nagano Prefecture. The operating company, Nagano Dentetsu, as well as the line itself, are most commonly referred to as 'Nagaden'.

The line has frequent services - both local and express - and acts as both a commuter route as well as a train link for the popular onsen in the Yamanouchi region, the Snow Monkey Park and the snow resorts of Shiga Kogen. The nearest ski lift of Shiga Kogen at Sun Valley is around 13km from Yudanaka Station.