The co-authors of this chapter discuss universal languages created from the seventeenth to the nineteenth century. Broadly defined, universal language schemes are artificially constructed languages used as auxiliary codes to facilitate communication, but they vary in the motivations for their creation and internal design. Usually, they are constructed to overcome language barriers, improve upon the irregularities of natural languages, and aim at easy learnability. Concerning their internal aspects, three types are distinguished: ‘universal characters’ (no use of sounds); simplified forms of existing languages; newly constructed languages (‘a priori ‘or ‘a posteriori’). With the decline of Latin, in the seventeenth century universal languages were popular and widely discussed in intellectual circles. They were ‘universal characters,' ‘real characters’ (the created words represented properties of things), ‘philosophical’ (Dalgarno, Wilkins) or aimed at guiding logical thinking (Leibniz). In late eighteenth century, philosophers/ideologues took interest in universal languages and ‘pasigraphies’ were invented. In thenineteenth century, universal languages developed in two directions: formal languages constructed by logicians, differing in structure from natural languages (Frege); international auxiliary languages — Volapuk, Esperanto — which, due to increasing internationalism, were successful. The idea of creating a universal language was supported by some prominent linguists.