The 1903 Rochester by-election was a Parliamentary by-election held on 23 September 1903. The constituency returned one Member of Parliament (MP) to the House of Commons of the United Kingdom, elected by the first past the post voting system.

Rochester was a parliamentary constituency in Kent. It returned two members of parliament (MPs) to the House of Commons of England from 1295 to 1707, then to the House of Commons of Great Britain from 1708 to 1800, and finally to the House of Commons of the Parliament of the United Kingdom from 1801 until the 1885 general election, when its representation was reduced to one seat.