Sectarian violence is the violence inspired by or between different sects of one religion. In contrast, religious violence is between different religions.

An example of sectarian violence was the fights between the Sunni Taliban sect of Islam and the Shia sect in Afghanistan. Another example between the Shia and Sunni sects of Islam are the bombings at in Pakistan.

The term is particularly frequently used to refer to the inter-communal conflict in Northern Ireland between 1972 and 2002. Nearly all the peopleliving in Northern Ireland identified themselves as belonging to either the Protestant or the (Roman) Catholic community. People of no religion and non-Christian faiths are still considered as belonging to one of the two "sects" along with churchgoers. In this context, "Protestants" means essentially descendants of immigrants from Scotland settled in Ulster during or soon after the 1690s; also known as "Loyalists" or "Unionists" because they generally support politically the status of Northern Ireland as a part of the United Kingdom. "Catholics" means descendants of the pre-1690 indigenous Irish population, who generally politically favour a united Ireland.

In many cases, the cause of violence is rarely only because of sectarian differences but is often also because of a power struggle or has social, or economic, or nationalistic aspects.

See also cult homicides