Kaisantunneli (Swedish: Kajsatunneln) is a tunnel for bicycle and pedestrian use in central Helsinki, Finland, serving as the main east–west cycling thoroughfare in the city centre.

[2] The tunnel is located directly underneath the Central Station, and joins the city's eastern and western cycling routes, cutting previous travel distance around the station by up to 600 metres (2,000 ft) and avoiding several sets of traffic lights, as well as removing much of the cycle traffic from the busy Kaivokatu street.

[3] Its western end connects directly to the Baana cycle path.

[1] The width of the tunnel is split roughly 50:50 between pedestrian and cycling lanes.

[4][1] The construction was especially challenging, on account of some old masonry and timber support structures underpinning the station, which were only discovered after construction had already begun.