An auxiliary language is one not the primary or native language of a community. It may refer to:

• Interlanguage, an idiolect that has been developed by a learner of a second language
• International auxiliary language, a planned language constructed for international communication, such as Esperanto or International Sign
• Zonal auxiliary language, a planned language focused on one particular region, often blending elements of somewhat related languages in that region
• Minority language, a secondary language that has official recognition
• Sacred language, also called liturgical language or initiation language, used in religious services
• Lingua franca, a language used to facilitate communication between groups without a common native language

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