Fritz Kater (12 December 1861 – 20 May 1945) was a German trade unionist active in the Free Association of German Trade Unions (FVdG) and its successor organization, the Free Workers' Union of Germany. He was the editor of the FVdG's organ Einigkeit and—after World War I—owner of the publishing houses Fritz Kater Verlag and Syndikalist. The son of a farmhand, Kater was born in 1861 in Barleben. His mother died when he was two years old. From the age of five, he had to work on the farm or at home in order to support his family. During his final two years in school, he also worked in a local sugar factory during the winter. Even after Kater started an apprenticeship as a mason, he still had to help his father on the farm as the elderly man was frequently ill. Only during the winter did Kater have spare time to read and educate himself. Fritz Reuter, a humorous poet who wrote in Low German, was his favorite writer. Kater joined the mason's trade union in Magdeburg in 1883 at a time when the Anti-Socialist Laws forbade most union activities. He came into contact with socialists from Berlin and Hamburg soon becoming a socialist himself under their influence. Kater soon began spending much of his spare time reading illegal socialist literature, and became active in the union's clandestine activities. In 1887, Kater joined the Social Democratic Party of Germany (SPD). In the same year he also founded a masons' union in Barleben, becoming the organization's first chairman. His unionist activities, which included trying to organize workers from the sugar factory he had worked in his youth, attracted resentment from the local authorities, especially from the head of the district authority, an extremely conservative Junker. In 1889 he was sentenced to a two-month prison term for holding an illegal meeting and in the following year he served even more time in jail for giving a speech held to be seditious. After the expiration of the Anti-Socialist Laws in 1890, Kater had close contacts with the opposition political movement Die Jungen, which was influenced by anarchist ideas. Kater was one of the founders of the Magdeburger Volksstimme, a social democratic newspaper started soon after the sunset of the Anti-Socialist Laws. The editors of the newspaper included several adherents of Die Jungen. At the 1891 Social Democratic Party (SPD) congress, Kater voted