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

• Americas:
  • Panama (then part of Colombia): Technically 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 true North American transcontinental railroad was completed in 1869, after track was laid over a 1,700 mile (2,700 km) gap between Sacramento and Omaha in six years by the Union Pacific and Central Pacific Railroads. Other transcontinental railroads followed, of which the Great Northern Railroad was built without federal aid by James J. Hill; it stretched from St. Paul to Seattle.
  • Canada: The Canadian Pacific Railway completed the first trans-Canada railway in 1885 and was the first seamless transcontinental system in North America. Two other transcontinental systems were built by the 1910s, the Canadian Northern Railway and the combined Grand Trunk Pacific Railway/National Transcontinental Railway; these were soon merged together into the Canadian National Railways, which remains Canada's "other" transcontinental railway to this day and the only railway north of Mexico to stretch from the shores of the Atlantic to the Pacific.
• 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 (5,787 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.