The National Union of Seamen (NUS) was the principal trade union of merchant seafarers in the United Kingdom from the late 1880s to 1990. In 1990, the union amalgamated with the National Union of Railwaymen to form the National Union of Rail, Maritime and Transport Workers (RMT).

The Seamen's Union was founded in Sunderland in 1887 as the National Amalgamated Sailors' and Firemen's Union. Its founder, J. Havelock Wilson became its president. It quickly spread to other ports and had become genuinely national by the end of 1888.

In 1888 and 1889 the union fought a number of successful strikes in Glasgow, Seaham, Liverpool and other major ports. By 1889, it had 45 branches and a nominal membership of 80,000. But from 1890, it began to face determined resistance from shipowners, who formed an association, the Shipping Federation, to co-ordinate their strike-breaking and anti-union activity. The union fought and lost defensive actions in Hull, Bristol, Cardiff and other important centres in 1891–1893. These episodes depleted its funds and led to a large fall in membership. The union also became involved in a large number of expensive legal cases. Although partly due to the actions of shipowners, the difficulties experienced by the union in this period have also been attributed to its officials' taste for litigation and their inadequate handling of union finances. In 1893, the NASFU went into voluntary liquidation to avoid bankruptcy.

Relaunched in 1894 as the National Sailors' and Firemen's Union (NSFU), having dropped the word "Amalgamated", the union continued to experience financial difficulties and low membership. From the summer of 1910 the union worked to promote a national seamen's strike to combat the Shipping Federation. This finally took place in the summer of 1911. The union's control over the movement was incomplete. In many ports rank and file strike committees and activists played a more important organisational role than the union itself, and the union's long-standing programme was over-shadowed by demands for wage increases. Nonetheless, the strike greatly increased both the funds and the membership of the union, allowing it to emerge once again as a significant force. Following the strike-wave, the union gained official recognition from many shipowners.

In 1911/1912 the growth of the NSFU was checked by a breakaway movement in Southampton and Glasgow which led to the formation of the rival British Seafarers' Union.^[2] At a national level, however, the NSFU was able to maintain and increase its supremacy.

Contemporaries often regarded the NSFU as a militant organisation because of the strikes in which it had involved itself in the late 1880s and in 1911. Yet from its inception the union expressed a belief in the possibility of industrial harmony, and announced itself in favour of establishing conciliation procedures. The leadership of the union was not greatly influenced by 'socialism'. Its founder and president, J. Havelock Wilson, served several terms as a Liberal Party MP, and the union itself did not affiliate to the Labour Party until 1919. Indeed, at the 1918 general election, it sponsored three candidates:^[3]

Wilson was primarily sponsored by the Liberal Party, while Bell described himself as a Coalition Labour candidate. Cathery ran in the name of the union.^[3]

After the outbreak of World War I, the union began collaborating closely with the Admiralty and shipowners in support of the war effort. From 1916, Havelock Wilson emerged as one of the most vehement supporters of the war in the labour movement, ostensibly because of Germany's conduct of the war at sea, especially the alleged targeting of non-combatant vessels. In 1917 the Union provoked controversy by refusing to convey Arthur Henderson and Ramsay MacDonald to a conference of socialist parties in Stockholm, which had been convened in the wake of the Russian Revolution to discuss the possibility of a peace policy.

A further development in 1917 was the formation of the National Maritime Board as a governing body for the merchant marine. The union's involvement in it allowed it to negotiate directly with shipowners over wages and conditions.

In 1922, the arrangements were extended by the establishment of the "PC5 system", which was intended to allow the Shipping Federation and the union to exercise joint control over access to employment in the shipping industry.

In 1921, the National Maritime Board imposed wage reductions, which were supported by the NSFU. The acceptance of cuts in pay provoked considerable resistance from ordinary seafarers and from the rival organisations: the British Seafarers' Union and the National Union of Ship's Stewards. Other sections of the trade union and labour movement were also strongly critical of the NSFU's detrimental collusion with employers. That was especially the National Transport Workers' Federation, which helped to merge the rival organisations referred to above into a new organisation, the Amalgamated Marine Workers' Union, intended as a viable alternative to the NSFU. Further wage reductions were made in 1923, and 1925, which again outraged members.

Militant resistance to the NSFU was expressed through the Seamen's Minority Movement (founded 1924) part of the Transport Workers' Minority Movement. Criticism of the NSFU became increasingly widespread with its apparent role in the 1925 Special Restriction (Coloured Alien Seamen) Order, which is seen as the first path-breaking attempt to expel non-British-born people;^[4] its failure to observe the general strike in 1926; and its support of a "non-political" Miners' Union in Nottinghamshire. In September 1928, the Union was officially expelled from the Trades Union Congress. However, after the death of Havelock Wilson in 1929, the NUS quickly began to pursue a more mainstream policy and became reconciled with the rest of the trade union movement. It adopted the title 'National Union of Seamen' in 1926. The term failed to recognise that women were also members; some seawomen had earlier organized in an unsuccessful Guild of Stewardesses.

By 1932, the Seamen's Minority Movement was 1,000-strong (less than a hundredth of the maritime workforce). Attempts were made among SMM black activists to combat the notorious postwar racism. Race riots had occurred in seaports such as South Shields, Liverpool and Cardiff. Also, the union itself felt a duty to support its white British-born members first during times of high unemployment. Key SMM figures in the 1920s and 1930s included Barbados-born, London-based Chris Braithwaite (Chris Jones). His connections with many antiracist initiatives including the Colonial Seamen's Organisation and the Pan-African Movement widened the SMM's links and brought international attention to the NUS's failure to back the largest black and minority ethnic workforce in Britain.^[5]

The NUS's almost-closed shop made the union stronger. After the Second World War there were widespread calls for reform of the NUS. Many members felt that the union was too closely associated with the employers and that it had failed to defend its members' interests. Rank and File Committees, building on the earlier Minority Movement, were established in many ports, and unofficial strikes took place in 1947, 1955 and 1960. A National Seamen's Reform Movement was established in the latter year.

A degree of reform was conceded in 1962, with the decision to allow a system of workplace representation by shop stewards. That belatedly brought the NUS into line with the general practices of the trade union movement. More importantly, it brought greater connection to the union. Seafarers could be away from home for months or years and so "a union man" on board, not far off in the Clapham headquarters, enhanced solidarity.

• Eastcote, Northamptonshire