An office in the priesthood. The scriptures speak of “high priest” in two senses: (1) an office in the Melchizedek Priesthood; and (2) under the law of Moses, the presiding officer of the Aaronic Priesthood.
The first sense applies to Jesus Christ as the great High Priest. Adam and all the patriarchs were also high priests. Today, three presiding high priests form the Presidency of the Church and preside over all other priesthood holders and Church members. Additional worthy men are ordained high priests as appropriate throughout the Church today. High priests may be called, set apart, and ordained as bishops (D&C 68:19; 107:69–71).
In the second sense, under the law of Moses, the presiding officer of the Aaronic Priesthood was called the high priest. The office was hereditary and came through the firstborn among the family of Aaron, Aaron himself being the first high priest of the Aaronic order (Ex. 28; 29; Lev. 8; D&C 84:18).