The National Union of Conservative and Unionist Associations (NUA) was established in 1867. Originally known as the National Union of Conservative and Constitutional Associations, it changed its name to the National Unionist Association of Conservative and Liberal-Unionist Organisations following the fusion of the Conservatives with the Liberal Unionists in 1912. In October 1924, it changed its name again to the National Union of Conservative and Unionist Associations.

It was designed originally as a means of organising the newly enfranchised working-class men in the boroughs, and was just one of a number of similar organisations and movements. Initially overshadowed by the Metropolitan Conservative Alliance and the Central Conservative Registration Association, the National Union was intended to be a federation of the many new Conservative Working Men's Associations which had sprung up since the franchise was extended by the 1867 Reform Act. It subsequently benefited greatly from being accommodated within Conservative Central Office in 1872, and the two thereafter worked closely together.

The number of Conservative associations affiliated to the National Union grew rapidly, from 289 in 1871 to 472 in 1875, and it eventually became a federation of all constituency associations, bringing together the rank and file of the Party in a national organisation. Representatives of the constituencies met at area and national level, and a system of advisory committees was used to convey grass roots opinion to the Party leadership. The National Union existed to express opinion and support and, as such, could exert a degree of influence on the Leader and over Party policy. It did not, however, possess any mandatory powers. The National Union was responsible for organising the annual Party Conference until 1993 when the responsibility was delegated to Central Office.

Following changes to the structure and organisation of the Party in March 1998, the National Union passed a resolution to suspend its activities. It was succeeded by the National Conservative Convention.