Fluency (also called volubility and loquaciousness) is the property of a person or of a system that delivers information quickly and with expertise.

Fluency is a speech language pathology term that means the smoothness or flow with which sounds, syllables, words and phrases are joined together when speaking quickly. "Fluency disorders" is used as a collective term for cluttering and stuttering. Both disorders have breaks in the fluidity of speech, and both have the fluency breakdown of repetition of parts of speech. Fluency disorders are most often complex in nature and they tend to occur more often in boys than in girls.

Language fluency is used informally to denote broadly a high level of language proficiency, most typically foreign language or another learned language, and more narrowly to denote fluid language use, as opposed to slow, halting use. In this narrow sense, fluency is necessary but not sufficient for language proficiency: fluent language users (particularly uneducated native speakers) may have narrow vocabularies, limited discourse strategies, and inaccurate word use. They may be illiterate, as well. Native language speakers are often incorrectly referred to as fluent.