Sir William John Polson KCMG (6 June 1875 – 8 October 1960) was a New Zealand politician, first as an Independent and then in the National Party.

He made a point of declining the United Party nomination, believing it more befitting that the leader of the Farmers' Union be non-partisan.

In 1936, following the election of the First Labour Government, Polson resigned as Farmers' Union president and joined the new National Party.

[2] Polson played a key role in replacing Adam Hamilton as National Party leader with Sidney Holland.

Thereafter Holland maintained Polson as a close confidant and he became Deputy Leader of the Opposition (an informal post at the time) as a sign to preserve unity between both the rural and urban sectors of the National Party.

During World War II he was a strong advocator that New Zealand forces should be deployed in the Pacific theatre, not Europe.