The Liberal Union () was a conservative liberal and progressive liberal political party in the Netherlands. A major party in its time, the Liberals were one of the historic predecessors of the Liberal State Party, and therefore of the People's Party for Freedom and Democracy.
After the Constitutional Reform of 1848, liberals became the dominant political force in the Netherlands. They were organised in loose political clubs and caucuses. Liberals were divided between progressive, centrist and conservative liberals, but because of the lack of organised political parties, these divisions were not very strong. In 1879 the division became explicit when a separate parliamentary party was formed by supporters of Jan Kappeyne van de Coppello. With the rise of both Catholic and Protestant parties, the liberals were forced to organise themselves better.
Development of the number of seats in the Lower House, of the 100 available. Before 1918 elected in single member districts, after that by proportional representation:
Liberal received support from atheist and Latitudinarian Protestant voters from the higher classes: businessmen, civil servants, wealthy farmers and voters from the liberal professions (lawyers, doctors, etc.) The party performed particularly well in the major trading cities Amsterdam and Rotterdam, in provincial centres like Arnhem, Zutphen and Leeuwarden, in the rich municipalities around Hilversum and The Hague and in northern rural provinces, like Groningen and Drenthe.
The Liberal Union formed a loose alliance with the League of Free Liberals and the Free-thinking Liberal League. The parties cooperated in several cabinets. The liberal legislation to extend suffrage and to better the position of workers was often supported by the Social Democratic Workers' Party.