Shingon Buddhism (真言宗, Shingon-shū^?) is one of the mainstream major schools of Japanese Buddhism and one of the few surviving Esoteric Buddhist lineages that started in the 3rd to 4th century CE that originally spread from India to China through traveling monks such as Vajrabodhi and Amoghavajra. The esoteric teachings would later flourish in Japan under the auspices of a Buddhist monk named Kūkai (空海), who traveled to Tang Dynasty China to acquire and request transmission of the esoteric teachings. For that reason, it is often called Japanese Esoteric Buddhism, or Orthodox Esoteric Buddhism. The word "Shingon" is the Japanese reading of the Kanji for the Chinese word Zhēnyán (真言), literally meaning "True Words", which in turn is the Chinese translation of the Sanskrit word mantra (मन्त्र).

Shingon Buddhist doctrine and teachings arose during the Heian period (794-1185) when a Buddhist monk named Kūkai traveled to China in 804 to study Esoteric Buddhist practices in the city of Xi'an (西安) (then called Chang-an), at Qinglong Temple (青龍寺, Blue Dragon Temple) under Master Huiguo, a favorite student of the legendary Amoghavajra and returned to Japan as his lineage and Dharma successor. Shingon followers usually address Kūkai as Kōbō-Daishi (弘法大師; lit. "Great Master of the Propagation of Dharma") or O-Daishi-sama (お大師様; "The Great Master"), the posthumous name given to him years after his death by Emperor Daigo.