A transcontinental railroad is a railway across a significant portion of a continent.

• Americas:
  • Panama (then part of Colombia): The first transcontinental railroad was the Panama Railway, completed in 1855. Near the narrowest point on the continent, it is only 48 miles long.
  • United States:
    • The First Transcontinental Railroad was the name of the first coast-to-coast railroad across the United States. It was completed in 1869, after track was laid over a 1,756 mile (2,826 km) gap between Sacramento and Omaha in six years by the Union Pacific and Central Pacific Railroads.
    • In 1882, the Atchison, Topeka and Santa Fe Railway, connected Atchison, Kansas with the Southern Pacific Railroad at Deming, New Mexico, thus completing a second link, to Los Angeles.
    • The Southern Pacific Railroad linked New Orleans with Los Angeles, in 1883, linking the Gulf of Mexico with the Pacific Ocean.
    • The Northern Pacific Railway, again completed in 1883, linked Chicago with Seattle.
    • The Great Northern Railroad was built without federal aid by James J. Hill; it stretched from St. Paul to Seattle.
  • Canada: Canada's transcontinental railway connection opened in 1885 when the Canadian Pacific Railway (CPR) completed a line to the Pacific coast. CPR became the first transcontinental railway company in North America in 1889 after its International Railway of Maine opened, connecting CPR to the Atlantic coast. Two other transcontinental lines were built in Canada: the Canadian Northern Railway (CNoR) opened another line to the Pacific in 1912, and the combined Grand Trunk Pacific Railway (GTPR)/National Transcontinental Railway (NTR) system opened in 1917 following the completion of the Quebec Bridge, although its line to the Pacific opened in 1914. The CNoR, GTPR, and NTR were nationalized to form the Canadian National Railways, which remains Canada's "other" transcontinental railway.
• Asia: The first Asian transcontinental railroad was the Trans-Siberian railway (with connecting lines in Europe), completed in 1905. It is the world's longest rail line at 9,289km (5,772 miles) long.
• Australia: The first trans-Australian railway was completed 1912. The first north-south trans-Australia railway opened in January 2004.
• Africa: There is no African transcontinental railroad. At least two trans-African projects have been planned: the Cape-Cairo railway by Cecil Rhodes on behalf of the British Empire, and a line from Abidjan to Algiers by the French.