More than 90 percent of Javanese are Muslims, on a broad continuum between abangan (more nominal or syncretic) and santri (more orthodox). Small Hindu enclaves are scattered throughout Java, but there is a large Hindu population along the eastern coast nearest Bali, especially around the town of Banyuwangi.

There are also Christian communities, mostly in the larger cities, though some rural areas of south-central Java are strongly Roman Catholic. Buddhist communities also exist in the major cities, primarily among the Chinese Indonesian. The Indonesian constitution recognizes six official religions.

Java has been a melting pot of religions and cultures, which has created a broad range of religious belief. Indian influences came first with Shivaism and Buddhism penetrating deeply into society, blending with indigenous tradition and culture. One conduit for this were the ascetics, called Resi, who taught mystical practices. A Resi would always be surrounded by their students, who took care of their master's daily needs. Resi's authorities was merely ceremonial. At the courts, Brahmin clerics and pudjangga (sacred literati) legitimised rulers and linked Hindu cosmology to their political needs.

Islam, which came after Hinduism, strengthened the status structure of this traditional religious pattern. The Muslim scholar of the writ (kyai) became the new religious elite as Hindu influences receded. Islam recognizes no hierarchy of religious leaders nor a formal priesthood, but the Dutch colonial government established an elaborate rank order for mosque and other Islamic preaching schools. In Javanese Islamic schools (pesantren), kyai prepertuated the tradition of resi. Students around him provided his needs, even peasants around the school.

Pre-Islamic Javanese traditions have encouraged Islam in a mystical direction. There emerged in Java a loosely structured society of religious leadership, revolving around kyais, possessing various degrees of proficiency in pre-Islamic and Islamic lore, dogma and practice. The kyais are the principal intermediaries between the villages masses and the realm of the supernatural. However, this very looseness of kyai leadership structure has promoted schism. There were often sharp divisions between orthodox kyais, who merely instructed in Islamic law, with those who taught mysticism and those who sought reformed Islam with modern scientific concepts. As a result, there is a division between santri, who believe that they are more orthodox in their Islamic belief and practice, with abangan, who has mixed pre-Islamic animistic and Hindu-Indian concepts with a superficial acceptance of Islamic dogma.

A wider effect of this division is the number of sects. In the middle of 1956, the Department of Religious Affairs in Yogyakarta reported 63 religious sects in Java other than the official Indonesian religions. Of these, 35 were in Central Java, 22 in West Java and 6 in East Java. These include Kejawen, Sumarah, Subud, etc. Their total membership is difficult to estimate as many of their adherents identify themselves with one of the official religions.
Two weeks in Myanmar
Cambodia itinerary 2 weeks
Mekong delta 3 day tour