Brahmarshi Vishvamitra (Sanskrit: विश्वामित्र, IAST: Viśvā-mitra) is one of the most venerated rishis or sages of ancient India.

A near-divine being, he is also credited as the author of most of Mandala 3 of the Rigveda, including Gayatri Mantra. The Puranas mention that only 24 rishis since antiquity have understood the whole meaning of—and thus wielded the whole power of—Gayatri Mantra.

Vishvamitra is supposed to be the first, and Yajnavalkya the last. Before renouncing his kingdom and royal status, Brahmarishi Vishvamitra was a king, thus he retained the title of Rajarshi or ‘royal sage’.