The concept of the Phineas Priesthood (or Phinehas Priesthood) comes from a 1990 book by white supremacist and Christian Identity follower Richard Kelly Hoskins, Vigilantes of Christendom: The Story of the Phineas Priesthood. Christian Identity is a racist and anti-Semitic sect whose adherents believe that white people are descended from the Lost Tribes of Israel. In his book, Hoskins describes a continuous priesthood of "avengers" who, throughout the centuries, have allegedly committed violent acts in order to defend racial purity and "God's Law." According to Hoskins, these avengers have been inspired by, and thus take their name from, an Old Testament figure Phineas who, in order to protect the purity of the Israelites and keep them from harm, killed a fellow Israelite who had taken up with a foreign woman.
In the early to mid-1990s, several bank robberies and bombings in Oklahoma and the Pacific Northwest by people who claimed to be Phineas Priests gave rise to the notion that the Phineas Priesthood actually existed as some sort of shadowy organization, but there has never been an organized Phineas Priesthood and there have been very few self-declared Phineas Priests committing violent actions. Rather, the notion of the Phineas Priesthood has come to be used symbolically by various hard-core Christian Identity adherents; it is now a meme more than anything else.
The main Phineas Priesthood symbol is a P with a horizontal line through it, symbolizing the spear of Phineas.