William Joseph Hopper, sometimes known as Will Hopper (born 9 August 1929) is a British investment banker who also became involved in the political field. He was one of the founders of the Institute for Fiscal Studies, a non-partisan research institute which offers comment on the economic impact of political proposals. Hopper enjoyed a brief political career as a Member of the European Parliament for the Conservative Party.
Hopper was brought up in Glasgow where he attended Langside Elementary School followed by Queen's Park Secondary School. He went to the University of Glasgow to read modern languages, and graduated with a 1st Class Master of Arts degree in 1953. He served in the Royal Air Force with the rank of Pilot Officer in the education branch from 1953 to 1955.
In 1956 Hopper joined W. R. Grace and Company in New York City to work as a financial analyst. After three years, he returned to Britain to be London office manager of H Hentz & Co, who were members of the . After six years he became general manager of S. G. Warburg & Co Ltd, and three years after that he was made a Director of Hill Samuel.
Hopper had discussed with three friends, all of whom were professional finance employees, the way in which Capital Gains Tax had been introduced in 1965, which all concerned thought had been disastrous. Over dinner in July 1968 the friends decided that what was needed was a non-partisan Institute which would research such proposals and report on them to the political world and the wider public; the Institute for Fiscal Studies was formally launched on 21 May 1969 with Hopper as founder chairman. The Institute also had undeclared objectives of improving procedures for changing taxation, and making taxation more rational. While at Hill Samuel, he became involved in examining the possibility of the Common Market developing a Common Capital Market which might include the United Kingdom; he knew this would transform the operation of the London capital markets. In 1975, Hopper left Hill Samuel to become a director of Morgan Grenfell. He was awarded the 'Deal of the Year' by Institutional Investor magazine in 1976 for his handling of a bond issue for the European Investment Bank.