Lord Hayagriva is the avatar of Lord Vishnu with the human body and a horse head. He is known as the God of knowledge and wisdom. His mantra is mentioned below to enhance intelligence power.
"Gnanananda Mayam Devam Nirmala Spatika krutim
Aadharam Sarva Vidyanaam Hayagreevam Upasmahe"
ज्ञानानन्दमयं देवं निर्मल स्फटिकाकृतिम्
आधारं सर्व विद्द्यानां हयग्रीवं उपास्महे
"Gnanananda Mayam Devam Nirmala Spatika krutim
Aadharam Sarva Vidyanaam Hayagreevam Upasmahe"
ज्ञानानन्दमयं देवं निर्मल स्फटिकाकृतिम्
आधारं सर्व विद्द्यानां हयग्रीवं उपास्महे
