Ukrainian Railways or Ukrzaliznytsia (UZ) (Ukrainian: Укрзалізниця) is a state-owned joint-stock company administering railway infrastructure and rail transport in Ukraine; a monopoly that controls the vast majority of the railroad transportation in the country. Ukrainian Railways is the world's sixth largest rail passenger transporter and world's seventh largest freight transporter. As of 2020, the total length of the main broad-gauge (1,520 mm) railroad network was 19,787 kilometres (12,295 mi), making it the 13th largest in the world. Ukraine also has many stretches of standard-gauge railway (1,435 mm), and is currently working to expand these in order to improve its connections to the European Union.

Railways with a railway track gauge of 5 ft first appeared in the United Kingdom and the United States. This gauge became commonly known as "Russian gauge", because the government of the Russian Empire chose it in 1843. Former areas and states of the Empire have inherited this standard. However in 1970, Soviet Railways re-defined the gauge as 1,520 mm.