Sutra (Sanskrit: सूत्र, romanized: sūtra, lit. 'string, thread') in Indian literary traditions refers to an aphorism or a collection of aphorisms in the form of a manual or, more broadly, a condensed manual or text. Sutras are a genre of ancient and medieval Indian texts found in Hinduism, Buddhism and Jainism.

In Hinduism, sutras are a distinct type of literary composition, a compilation of short aphoristic statements. Each sutra is any short rule, like a theorem distilled into few words or syllables, around which teachings of ritual, philosophy, grammar, or any field of knowledge can be woven. The oldest sutras of Hinduism are found in the Brahmana and Aranyaka layers of the Vedas. Every school of Hindu philosophy, Vedic guides for rites of passage, various fields of arts, law, and social ethics developed respective sutras, which help teach and transmit ideas from one generation to the next.

In Buddhism, sutras, also known as suttas, are canonical scriptures, many of which are regarded as records of the oral teachings of Gautama Buddha. They are not aphoristic, but are quite detailed, sometimes with repetition. This may reflect a philological root of sukta (well spoken), rather than sutra (thread).

In Jainism, sutras, also known as suyas, are canonical sermons of Mahavira contained in the Jain Agamas as well as some later (post-canonical) normative texts.