Shinbutsu-shūgō (神仏習合, "syncretism of kami and buddhas"), also called Shinbutsu shū (神仏宗, "god buddha school") Shinbutsu-konkō (神仏混淆, "jumbling up" or "contamination of kami and buddhas"), is the syncretism of Shinto and Buddhism that was Japan's main organized religion up until the Meiji period. Beginning in 1868, the new Meiji government approved a series of laws that separated Japanese native kami worship, on one side, from Buddhism which had assimilated it, on the other.
When Buddhism was introduced from China in the Asuka period (6th century) the Japanese tried to reconcile the new beliefs with the older Shinto beliefs, assuming both were true. As a consequence, Buddhist temples (寺, tera) were attached to local Shinto shrines (神社, jinja) and vice versa and devoted to both kami and buddhas. The local religion and foreign Buddhism never quite fused, but remained inextricably linked to the present day through interaction. The depth of the influence from Buddhism on local religious beliefs can be seen in much of Shinto's conceptual vocabulary and even the types of Shinto shrines seen today. The large worship halls and religious images, are themselves of Buddhist origin. The formal separation of Buddhism from Shinto took place only as recently as the end of the 19th century; however, in many ways, the blending of the two still continues.
The term shinbutsu shūgō itself was coined during the early modern era (17th century) to refer to the amalgamation of kami and buddhas in general, as opposed to specific currents within Buddhism which did the same, e.g. Ryōbu Shintō and Sannō Shintō. The term may have a negative connotation of bastardization and randomness. It is a yojijukugo phrase.
There is no agreement among specialists as to the exact extent of fusion between the two religions.
According to some scholars (for example, Hirai Naofusa in Japan and Joseph Kitagawa in the US), Shinto is the indigenous religion of Japan, has existed as such continuously since its prehistory, and consists of all the peculiarly Japanese rituals and beliefs shaped by Japanese history from prehistory to the present.