Sir William Thomas White KCMG PC (13 November 1866 – 11 February 1955), was a Canadian politician and Cabinet minister.

As finance minister, White introduced the income tax to help fund Canada's World War I efforts.

White did not hold a seat in the House of Commons of Canada at the time, and in fact had never campaigned for public office before.

Nevertheless, he was elected by acclamation in a by-election in the eastern Ontario riding of Leeds, after another Conservative Member of Parliament (MP) was convinced to resign.

His approach was conservative, and he was reluctant to interfere with private enterprise or even to raise taxes in the early period of the war.

Although he eventually made some interventions (including fixed profit margins and regulated food supplies), he continued to reject fundamental changes in the nation's finances.

Later in the year, he published a pamphlet entitled The Story of Canada's War Finances, defending his management of the wartime economy.