What is the world's longest railway tunnel (as of 2025)?

As of 2025, the world’s longest railway tunnel is Switzerland’s Gotthard Base Tunnel.

The tunnel runs for about 57.1 kilometres beneath the Swiss Alps, connecting Erstfeld in the canton of Uri with Bodio-area routes in Ticino. It forms the low-level centrepiece of Switzerland’s New Railway Link through the Alps, designed to improve north–south passenger and freight connections between northern Europe and Italy.

Construction officially began in 1999, and the tunnel opened in 2016. It consists of two parallel single-track tubes connected by cross-passages, allowing trains to travel on a comparatively flat route instead of climbing the older Gotthard railway line. The lower alignment supports faster passenger services and longer, heavier freight trains.

The Gotthard Base Tunnel is often confused with the older Gotthard Tunnel, which opened in 1882 and is roughly 15 kilometres long. Another frequent mix-up involves the Channel Tunnel: it is a major rail tunnel beneath the English Channel, but at about 50.5 kilometres it is shorter overall than the Gotthard Base Tunnel. “Longest railway tunnel” also differs from longest tunnel of any purpose.