The rail transport system in Denmark consists of 2,633 km of railway lines, of which the Copenhagen S-train network, the main line Helsingør-Copenhagen-Padborg (at the German border), and the Lunderskov-Esbjerg line are electrified. Most traffic is passenger trains, although there is considerable transit goods traffic between Sweden and Germany.

Maintenance work on most Danish railway lines is done by Banedanmark, a state-owned company that also allocates tracks for train operators. The majority of passenger trains are operated by DSB, with Arriva operating on some lines in Jutland. Goods transport is mainly performed by DB Schenker Rail, although other operators take care of a significant portion of the non-transit traffic.

Denmark is a member of the International Union of Railways (UIC). The UIC Country Code for Denmark is 86.

Banedanmark is in charge of 2,132 km of railway lines, which do not include the lines controlled by private railways. All Danish railways are 1,435 mm (4 ft 8 ¹⁄₂ in) (standard gauge), with the exception of a few narrow gauge museum railways; 1,000 mm (3 ft 3 ³⁄₈ in) gauge was previously common on branch lines, with 700 mm (2 ft 3 ⁹⁄₁₆ in) being prevalent on industry railways, such as those for transporting sugar beets. The narrow gauge lines generally disappeared during the 1950s and 1960s.

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