"Son of God" is a phrase which, according to most Christian denominations Trinitarian in belief, refers to the divine relationship between Jesus and God, specifically as "God the Son". To a minority of Christians, nontrinitarians, the term "Son of God", applied to Jesus in the New Testament, is accepted, while the non-biblical but less ambiguous "God the Son" is not.
Throughout history, emperors have assumed titles that amount to being "a son of god", "a son of a god" or "son of Heaven". Roman Emperor Augustus referred to his relation to the deified adoptive father, Julius Caesar as "son of a god" via the term divi filius which was later also used by Domitian and is distinct from the use of Son of God in the New Testament.
In the New Testament, the title "Son of God" is applied to Jesus on many occasions. It is often seen as referring to his divinity, from the beginning in the Annunciation up to the Crucifixion. The declaration that Jesus is the Son of God is made by many individuals in the New Testament, and on two separate occasions by God the Father as a voice from Heaven, and is asserted by Jesus himself.