In Hindu tradition, which Veda contains the Gayatri mantra?

In Hindu tradition, the Gayatri mantra is found in the Rigveda.

The Gayatri mantra is one of the best-known Vedic hymns. Its earliest textual form appears in Rigveda 3.62.10, where it is addressed to Savitr, a solar deity. The mantra asks for divine illumination of the intellect and is composed in the gayatri meter, a Vedic poetic meter associated with three lines of eight syllables each.

The hymn is traditionally connected with the sage Vishvamitra, who is credited with the surrounding Rigvedic passage in many Hindu accounts. It later became especially important in upanayana initiation and in daily recitation practices. Although the mantra is from the Rigveda, it is also quoted, adapted, and chanted in many later Hindu traditions, which can lead to confusion about its source. Samaveda is primarily known for musical arrangements of verses, Yajurveda for sacrificial formulas, and Atharvaveda for varied hymns and ritual material.