John Ignatius Armstrong AC was an Australian politician and diplomat. He served as a Senator for New South Wales from 1938 to 1962, representing the Labor Party, and was a minister in the Chifley government. Armstrong later served as Lord Mayor of Sydney from 1965 to 1967, and then as High Commissioner to the United Kingdom from 1973 to 1974.

The Second Chifley ministry (Labor) was the 33rd ministry of the Government of Australia. It was led by the country's 16th Prime Minister, Ben Chifley. The Second Chifley Ministry succeeded the First Chifley ministry, which dissolved on 1 November 1946 following the federal election that took place in September. The ministry was replaced by the Fourth Menzies ministry on 19 December 1949 following the federal election that took place on 10 December which saw the Liberal–Country Coalition defeat Labor.