New Zealand statesman who, as minister of lands (1891–1900), sponsored legislation that provided land and credit to small farmers and helped to break up large estates.

McKenzie's deep antagonism toward land monopolists was rooted in his boyhood in Scotland, where he witnessed the dispossession of small farmers by Highland landlords. After immigrating to New Zealand in 1860, he farmed and served in the Otago provincial council (1871–76). Elected to Parliament as an independent in 1881, he was legislative whip for the ministry of Sir Robert Stout (1884–87) and was named minister of lands and agriculture in 1891 by Liberal Prime Minister John Ballance, who shared McKenzie's determination to create opportunities for small farmers.

In 1892 McKenzie won passage of the Lands for Settlement Act that opened up crown land for leasing and, when amended in 1894, compelled owners of large estates to sell portions of their holdings. Also in 1894 he introduced the Government Advances to Settlers Act, which greatly expanded the supply of credit available to farmers, and he sponsored a plan for unemployed workers to clear and then lease landholdings. He promoted scientific methods in agriculture, and by the time of his retirement in 1900 he had laid the foundations for the present Ministry of Agriculture. He was knighted in 1901.