The Letten Tunnel was a railway tunnel in the Swiss city of Zurich. It formed part of the old route of the Lake Zurich right bank railway from Zürich Hauptbahnhof railway station to Rapperswil station. Radical changes to the local railway geography led to the tunnel being disused in 1989, tracks removed by 2002, and finally filled in from 2002-2004 due to its poor condition.