The National Union of Insurance Workers (NUIW) was a trade union representing workers in the insurance industry in the United Kingdom.
The union was formed in 1964, when the National Amalgamated Union of Life Insurance Workers merged with the National Federation of Insurance Workers. Initially, the union operated as a federation, with affiliates representing workers at larger individual companies, and a Composite Section for workers at smaller companies. Several of these sections left in the 1970s to join the Association of Scientific, Technical and Managerial Staffs. Three sections remained, representing workers at the Prudential, Liverpool Victoria and the Royal London, and these merged into the central union in 1984.
The union's membership fell over the years, from 25,740 in 1974, to only 12,519 in 1993. In 2000, it merged into the Manufacturing, Science and Finance trade union.