John Scaddan, CMG (4 August 1876 – 21 November 1934), popularly known as "Happy Jack", was Premier of Western Australia from 7 October 1911 until 27 July 1916.

Scaddan initially worked underground as a miner, but after gaining his engine-driver's certificate, he operated a stationary engine at the pit head.

In addition, land taxation was increased, a graduated income tax was introduced, and considerable reforms were carried out in the fields of divorce, criminal law, irrigation, and education.

Scaddan's government became involved in numerous industries: it established a state shipping service; started a dairy farm at Claremont and a sawmill at Manjimup; reopened a quarry at Boya; set up a brickworks and an agricultural implement works; took over the South Perth ferries and Perth's trams; started up abattoirs; and even purchased hotels.

To help finance its policies, Scaddan's government introduced an income tax in 1912, and this was greatly increased after World War I broke out.

This small majority, along with the outbreak of war in 1914 and the onset of one of the worst droughts ever to hit Western Australia, severely restricted Scaddan's policy in his second term.

The government's position was made even more unstable when, in January 1915, the Labor MLA for Roebourne, Joseph Gardiner, walked out of Parliament House, and did not return.

Meanwhile, Bertie Johnston, Labor's only member for a farming seat, had voted with the opposition several times in reaction to Scaddan's failure to fulfill a promise to reduce the price of crown land.

However, the federal Labor Party split in 1916 over the issue of conscription, and it was inevitable that this would eventually affect the Western Australian branch.

With the May 1917 elections approaching, Scaddan found himself in the untenable position of supporting the non-Labor Prime Minister Hughes instead of the Labor Party leader Frank Tudor.

Scaddan was appointed Minister for Mines and Railways in Lefroy's Nationalist government on 28 June 1917, but Lutey defeated him in the ministerial by-election.

On 17 May 1919, Scaddan was appointed Colonial Secretary and Minister for Railways in James Mitchell's government, despite not being a member of either house of parliament.

He won the seat of Maylands in the election of May 1930, upon which he was appointed Minister for Railways, Mines, Police, Forests and Industry in the Mitchell government.