Mary Victoria Cracroft Grigg, Lady Polson, MBE (18 August 1897 – 22 December 1971) was a New Zealand politician of the National Party.
She was born as Mary Victoria Cracroft Wilson at Culverden in 1897. Her parents were John Wilson, a sheepfarmer, and Mildred Hall. Her paternal grandfather was John Cracroft Wilson, and her maternal grandfather was John Hall; both had been prominent MPs. Her mother was known for her involvement with public activities, particularly those involving women.
Mary was educated for eight years at the Brondesbury School in London, where she became a head girl. During the First World War she served in the nursing division of the VAD (Voluntary Aid Division).
In 1941 Grigg was elected onto the Ashburton Hospital Board and became its first woman member. She was also president of the Ashburton Plunket Society, a member of the Red Cross executive and President of the Mount Somers Ladies' Guild. When her husband Arthur Grigg rejoined the army, she took over his parliamentary duties in the electorate.
She was elected to represent the Mid-Canterbury electorate in Parliament from 1942 after the death (on 29 November 1941) of her husband Arthur Grigg in a political practice known as widow's succession. She had married Grigg in 1920, and he had held the Mid-Canterbury electorate from 1938
Her greatest area of concern was farming issues, followed by housing, health and education. In 1942 she joined with other women MPs from both sides of the House to argue that the number of women police officers should be increased and that they should be issued with a uniform. She also campaigned for women to be permitted to sit on juries.