Joseph (Jo) Grimond, Baron Grimond (July 29, 1913 - October 24, 1993) was a British politician, leader of the Liberal Party from 1956 to 1967 and again briefly in 1976.

Grimond was educated at Eton College and Balliol College, Oxford, became a barrister, and in 1938 married Laura Bonham-Carter, a granddaughter of Herbert Asquith. After service in World War II, he entered parliament in 1950 as Liberal member for Orkney and Shetland, continuing to represent the constituency until he retired from politics in 1983. He was a life-long champion of Scottish devolution within the UK, and although he was often wary of the bureaucracy of theEuropean Economic Community (EEC), was an early advocate of the EEC.

Grimond led the party through a difficult period in the late 1950s and early 1960s. The party he inherited commanded barely 2.5% of the vote. A man of considerable personal charm, charisma, and intelligence he was widely respected and inspired trust, and by the end of his tenure the Liberal party was once more a mainstream party. It was during his leadership that the first post-war Liberal revival took place- under Grimond the Liberals doubled their seats and won historic by-elections in Torrington (1958), Orpington (1962), and Roxburgh, Selkirk and Peebles (1965). In 1967, he made way for a younger, more dynamic leader, Jeremy Thorpe. In 1976, when Thorpe was forced to resign because of a scandal, Grimond stepped in as caretaker leader until the election of a replacement, David Steel.

Among other posts, Grimond was a barrister and publisher in the 1930s, an army major during World War II, Secretary of the National Trust for Scotland from 1947 to 1949, and held the Chancellorships of the University of Edinburgh and the University of Kent. His many books include The Liberal Future (1959, credited with reinvigorating radical liberalism as a coherent modern ideology), The Liberal Challenge (1963), and Memoirs (1979). On leaving parliament, he was created a life peer (Baron Grimond, of Firth in the County of Orkney). He remained devoted to his former parliamentary constituency, and was buried in the Orkneys.

Jo Grimond was survived by his widow Laura. Laura was the wife then widow of a Life Peer, the sister of another Life Peer, the daughter of a Life Peeress, and the great-granddaughter of a hereditary peer of first creation.

He had three children:

• Grizel Grimond, who had a daughter by the actor Sir Tony Richardson.
• John Grimond, a foreign editor of The Economist who was married 1973 to Katherine "Kate" Fleming, elder daughter of Peter Fleming and the actress Celia Johnson, and had three children with her.
• Magnus Grimond, a merchant banker.