Universal language may refer to a hypothetical or historical language spoken and understood by all or most of the world's people. In some contexts, it refers to a means of communication said to be understood by all humans. It may be the idea of an international auxiliary language for communication between groups speaking different primary languages. In other conceptions, it may be the primary language of all speakers, or the only existing language. Some religious and mythological traditions state that there was once a single universal language among all people, or shared by humans and supernatural beings.

In other traditions, there is less interest in or a general deflection of the question. The written Classical Chinese language is still read widely but pronounced differently by readers in China, Vietnam, Korea and Japan; for centuries it was a de facto universal literary language for a broad-based culture. In something of the same way Sanskrit in India and Nepal, and Pali in Sri Lanka and in Theravada countries of South-East Asia (Burma, Thailand, Cambodia) and Old Tamil in South India and Sri Lanka, were literary languages for many for whom they were not their mother tongue.

Comparably, the Latin language (qua Medieval Latin) was in effect a universal language of literati in the Middle Ages, and the language of the Vulgate Bible in the area of Catholicism, which covered most of Western Europe and parts of Northern and Central Europe also.

In a more practical fashion, trade languages, such as ancient Koine Greek, may be seen as a kind of real universal language, that was used for commerce.

In historical linguistics, monogenesis refers to the idea that all spoken human languages are descended from a single ancestral language spoken many thousands of years ago.