Despite its potential significance, firstborn-son Christology has not yet been a major research focus of New Testament Christology in current scholarship. This work offers a study of the meaning of the firstborn son (πρωτότοκος) in the New Testament (Rom 8:29; Col 1:15, 18; Heb 1:6, Rev 1:5; cf. Heb 12:23) paying specific attention to the concept of the firstborn in the Old Testament and Jewish literature. The study argues that primogeniture was a unique institution in Jewish society and the firstborn son was the principal heir of the father's inheritance. In the Old Testament and Jewish literature, the title of the firstborn son refers to the heir of divine promise and is employed to formulate the self-perception of Israel in terms of its primacy and inheritance. Thus, the title of the firstborn son indicates his access to the promise of Israel, and is associated with the right of the inheritance (i.e., primogeniture) including the Land and the special status of Israel. In the New Testament, the motif of the firstborn son signals that the promise given to Israel as the firstborn son was fulfilled in Christ and the Christian community.