The Cornish rotten and pocket boroughs were one of the most striking anomalies of the Unreformed House of Commons in the Parliament of the United Kingdom before the Reform Act 1832. Immediately before the Act, Cornwall had twenty boroughs, each electing two members of parliament, as well as its two knights of the shire, a total of 42 members, far in excess of the number to which its wealth, population or other importance would seem to entitle it. Until 1821, there was yet another borough which sent two men to parliament, giving Cornwall only one fewer member in the House of Commons than the whole of Scotland.
Most of these were rotten boroughs, a term meaning communities which had decreased in size and importance since the Middle Ages and were too small to justify separate representation. The rest were pocket boroughs, in which a "patron" owned enough of the tenements which carried a vote that he was able to choose both members. The patron's nominees were usually returned unopposed, as anyone standing against them was sure to lose.