1821 in rail transport

April event

 * April 19 – Stockton and Darlington Railway is authorised by the Parliament of the United Kingdom.

November event

 * November – Henry Robinson Palmer patents a monorail system in England.

May births

 * May 8 – William Henry Vanderbilt, son of Cornelius Vanderbilt and president of the New York Central system (d. 1885).

August births

 * August 10 – Jay Cooke, financier who built the Northern Pacific Railway (d. 1905).
 * August 17 – John Saxby, English railway signalling engineer (d. 1913).

October births

 * October 21 - Collis P. Huntington, a member of The Big Four group of financiers in California (d. 1900).

December births

 * December 17 - Frederick W. Lander, Chief Civil Engineer for the Pacific Railroad (d. 1862).