The Cato Street Conspiracy was a plot to murder all the British cabinet ministers and the Prime Minister Lord Liverpool in 1820. The name comes from the meeting place near Edgware Road in London. The police had an informer; the plotters fell into a police trap. Thirteen were arrested, while one policeman, Richard Smithers, was killed. Five conspirators were executed, and five others were transported to Australia.

How widespread the Cato Street conspiracy was is uncertain. It was a time of unrest; rumours abounded. Malcolm Chase noted that "the London-Irish community and a number of trade societies, notably shoemakers, were prepared to lend support, while unrest and awareness of a planned rising were widespread in the industrial north and on Clydeside."