The Brenner Base Tunnel (; ) is a railway tunnel under construction through the base of the Eastern Alps beneath the Brenner Pass. Upon completion, it will be the second longest railway tunnel in the world, surpassing the Seikan tunnel by over a kilometre. It will run from near Innsbruck, in Austria, to Fortezza, in Italy, replacing part of the current Brenner railway. The line is part of Line 1, the Berlin to Palermo route, of Trans-European Transport Networks (TEN-T).