The International Workingmen's Association (IWA), often called the First International (1864–1876), was an international organisation which aimed at uniting a variety of different left-wing socialist, communist and anarchist groups and trade unions that were based on the working class and class struggle. It was founded in 1864 in a workmen's meeting held in St. Martin's Hall, London. Its first congress was held in 1866 in Geneva.
In Europe, a period of harsh reaction followed the widespread Revolutions of 1848. The next major phase of revolutionary activity began almost twenty years later with the founding of the IWA in 1864. At its peak, the IWA reported having 8 million members while police reported 5 million. In 1872, it split in two over conflicts between statist and anarchist factions and dissolved in 1876. The Second International was founded in 1889.
Following the January Uprising in Poland in 1863, French and British workers started to discuss developing a closer working relationship. Henri Tolain, Joseph Perrachon and Charles Limousin visited London in July 1863, attending a meeting in St. James's Hall in honour of the Polish uprising. They discussed the need for an international organisation, which would amongst other things prevent the import of foreign workers to break strikes. In September 1864, French and British delegates again met in London, this time to set up an organization for sharing labor information across borders.
On 28 September an international crowd of workers gathered to welcome the French delegates in St Martin's Hall in London. Among the many European radicals were English Owenites, followers of Pierre-Joseph Proudhon and Louis Auguste Blanqui, Irish and Polish nationalists, Italian republicans and German socialists. Included among the last-mentioned of this eclectic band was a somewhat obscure 46-year-old émigré journalist Karl Marx, who would soon come to play a decisive role in the organisation.
The positivist historian Edward Spencer Beesly, a professor at London University, was in the chair.