Herbert W. Armstrong was an American evangelist who founded the Worldwide Church of God (WCG). An early pioneer of radio and television evangelism, Armstrong preached what he claimed was the comprehensive combination of doctrines in the entire Bible, in the light of the New Covenant scriptures, which he maintained to be the restored true Gospel. These doctrines and teachings have been referred to as Armstrongism by non-adherents.

Armstrongism is the teachings and doctrines of Herbert W. Armstrong while leader of the Worldwide Church of God (WCG). His teachings are professed by him and his followers to be the restored true Gospel of the Bible. Armstrong said they were revealed to him by God during his study of the Bible. The term Armstrongite is sometimes used to refer to those that follow Armstrong's teachings. Armstrongism and Armstrongite are generally considered derogatory by those to whom it is applied, who prefer to be known as members of the Church of God (COG). These doctrines were also espoused by his sons Richard David Armstrong and Garner Ted Armstrong with slight variations.