Stuttgart 21 is a railway and urban development project in Stuttgart, Germany. It is a part of the Stuttgart–Augsburg new and upgraded railway and the Main Line for Europe (Paris—Vienna) within the framework of the Trans-European Networks. Its core is a renewed Stuttgart Hauptbahnhof, among some 57 kilometres (35 miles) of new railways, including some 30 kilometres (19 miles) of tunnels and 25 kilometres (16 miles) of high-speed lines.
The project was officially announced in April 1994. Construction work began on 2 February 2010.[2] In March 2013, total costs were officially estimated at €6.5 billion, the previous estimate being €4.5 billion in 2009.[2] In March 2022, Deutsche Bahn estimated the total cost at €9.15 billion.[3] Heated debate ensued on a broad range of issues, including the relative costs and benefits, geological and environmental concerns, as well as performance issues.
In 2019, operations had been expected to start in December 2025,[4] delayed from the initial estimation of 2019 (made in 2010). In 2024, the opening date for main elements of the project was delayed again, to December 2026.[5]