John Blyth Hayes CMG (21 April 1868 – 12 July 1956) was an Australian politician who served as a Senator for Tasmania from 1923 to 1947.

He was the son of Elizabeth (née Blyth) and Joshua John Hayes, his father being a farmer.

He participated in the Western Australian gold rushes, and eventually became the manager of an ore-reduction facility and cyanide works at Wiluna.

[2] The Nationalists were reduced to a minority government at the 1922 state election, due to the success of the newly formed Country Party led by Hayes' brother-in-law Ernest Blyth.

[1][2] After losing the premiership, Hayes nominated to fill the casual vacancy caused by the death of Senator Thomas Bakhap.

His election meant that the positions of President of the Senate, Speaker of the House of Representatives, and Prime Minister were all held by Tasmanians (George John Bell being the incumbent speaker and Joseph Lyons the incumbent prime minister).

Hayes faced several motions of dissent in the early days of his presidency, but his rulings later achieved widespread acceptance.

Although the government had a nominal majority in the Senate, Allan MacDonald had been taken ill and Keith Wilson was absent overseas on military duty.