Vishvamitra
Brahmarshi Vishvamitra (Sanskrit: विश्वामित्र viśvā-mitra "friend of the world"; Kannada: ವಿಶ್ವಾಮಿತ್ರ; Malayalam: വിശ്വാമിത്രൻ; Telugu: విశ్వామిత్ర; Tamil: விஸ்வாமித்திரன் Visvāmittiraṉ; Thai: Swamit; Burmese: Bodaw; Javanese: Wiswamitra) is one of the most venerated rishis or sages of ancient times in India. He is also credited as the author of most of Mandala 3 of the Rigveda, including the Gayatri Mantra. The Puranas mention that only 24 rishis since antiquity have understood the whole meaning of, and thus wielded the whole power of, the Gayatri Mantra. Vishvamitra is supposed to be the first and Yajnavalkya the last.
Read more about Vishvamitra: Kaushika, Conflict With Vasistha, Tapasya, Rise To Brahmarishi, Vishvamitra's Characteristics, Gayatri Mantra, Vishvamitra in Buddhism