Joseph Paton Maclay, 2nd Baron Maclay KBE (31 May 1899 – 7 November 1969), was a Scottish banker, shipowner, peer and Liberal politician.
He was elected to the House of Commons as Member of Parliament (MP) for Paisley in 1931, a seat he held until the 1945 general election.
In 1951, he succeeded his father in the barony and entered the House of Lords. Maclay was elected as a Liberal in support of the National Government and prime minister Ramsay MacDonald. When the Liberal Party led by Sir Herbert Samuel withdrew from the coalition in November 1933, Maclay refused to cross the floor into opposition with Samuel. However he never seems to have taken the whip of the Liberal National Party, the group in Parliament led by Sir John Simon.
At the 1935 general election he was re-elected in Paisley as a Liberal, although as in 1931 he had no Conservative opponent. This was because he did generally tend to support the government. In the crucial vote after the Norway debate on 8 May 1940 which led to the downfall of Neville Chamberlain he was one of only two Liberals to support the government (the other was Gwilym Lloyd George). Despite this, his personal relations with Herbert Samuel must have remained cordial as he was invited by Samuel to accompany him to a conference of the Institute of Pacific Relations held in Banff in Canada during the summer recess of 1933 to act as an honorary private secretary and before the conference they enjoyed some walking together in the forested countryside around Lake Louise (Alberta).
During the Second World War, Maclay followed similar footsteps to those his father had trod in the Great War, when he was appointed Head of the Convoy and Admiralty Liaison, in the Ministry of War Transport between 1943 and 1945.