The HSL-Zuid (Dutch: Hogesnelheidslijn Zuid, English: High-speed Line South), is a 125 kilometre-long (78 miles) Dutch high-speed railway line running between the Amsterdam metropolitan area and the Belgian border, with a branch to Breda, North Brabant. Together with the Belgian HSL 4 it forms the Schiphol–Antwerp high-speed railway. Originally scheduled to be in service by 2007, the first public operations began on 7 September 2009, after a ceremony on 6 September.

Intercity Direct operates between Amsterdam and Breda, for the time being with conventional Intercity carriages and TRAXX locomotives. On 13 December 2009 Thalys began services from Amsterdam to Paris and Brussels on the HSL-Zuid. On 4 April 2018 the first scheduled Eurostar connected Amsterdam to London via the HSL-Zuid.

Talks about a high-speed line between Amsterdam and the Belgian border started under Prime Minister Joop den Uyl (1973–1977); work began during Wim Kok's first term (1998–2002). The Rijkswaterstaat, a government agency under the authority of the Ministry of Transport and Water Management, was responsible for the organisation of the project. The Government of the Netherlands awarded the country's largest ever public-private partnership (PPP) contract to the consortium Infraspeed until 2030; it is responsible for design, construction, financing and maintenance. The line features state-of-the-art technology, including ETCS L2 train control systems provided by Siemens AG and Alcatel (activities now part of Thales), and will be an ERTMS 2.3.0 Corridor.