Sir John Rigby, PC (8 January 1834 – 26 July 1903), was a British judge and Liberal politician who sat in the House of Commons between 1885 and 1894.
Rigby was born in Runcorn, Cheshire, the son of Thomas Rigby of Halton, Cheshire, and his wife Elizabeth Kendal. He attended Liverpool College before going to Trinity College, Cambridge in 1853. He graduated as Second Wrangler in 1856, also being placed second for the Smith's Prize. He became a fellow of Trinity in 1856 and was called to the Bar at Lincoln's Inn in 1860.
In 1875 Rigby was appointed junior counsel to the Treasury. In 1881 he "took silk", becoming a Queen's Counsel. He distinguished himself as an advocate, and was frequently involved in bringing appeals to the judicial committee of the House of Lords. Rigby was twice briefly a Liberal Party Member of Parliament. He was elected as MP for the Wisbech division of Cambridgeshire at the 1885 general election, but lost the seat when another election was held in 1886.
In 1892 Rigby returned to parliament, when he was among a number of Liberals who gained seats from the government parties in Scotland. He was elected at Forfarshire, unseating the Liberal Unionist, James Barclay. He was appointed Solicitor General for England and Wales in William Gladstone's new government, and received a knighthood on 26 November 1892. On 3 May 1894 Rigby became Attorney General for England and Wales.