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 joined the National Party on its formation in 1936, and "later acted effectively as Holland's deputy".
He represented the electorate of Stratford in Parliament from 1928 to 1946, when he retired. He was appointed to the Legislative Council on 15 March 1950, as a member of the suicide squad which was to vote the Council out of existence.
Polson was born in Wanganui, and educated at Wanganui Collegiate School. In 1943 he married Mary Grigg, who had represented the Mid-Canterbury electorate from 1942, after her MP husband Arthur Grigg, then a major in the NZEF, was killed in Libya in 1941.
In 1935, Polson was awarded the King George V Silver Jubilee Medal. In the 1951 King's Birthday Honours he was appointed a Knight Commander of the Order of St Michael and St George for public and political services.