The paper presents a marble bust depicting a Salvator mundi offered at a Sotheby's London auction of 2010 with a “Circle of Pietro Bernini” attribution and currently in a private collection in New York. We propose that the sculpture (datable by style to circa 1617-19), as yet unpublished in the scholarly literature, was undoubtedly executed by Pietro Bernini but that the invention, composition, and probably the models be recognized as the work of the young but already affirmed Gian Lorenzo. The bust displays a new focus, an unknown solidity, and a palpable interior life that prompted presentation of Christ as the story of a character, almost a biography, or at least as an individual psychology, and therefore as a portrait, not an object or a whimsical still life in marble. The Christ is planned and 'built' like a portrait though Pietro probably had never before sculpted a portrait (at least we know of none), and had always remained diligently within the bounds of established genres. This 'portrait of Christ' tends instead to supersede those boundaries taking advantage of the great lesson of the contemporary painting of Annibale Carracci and Caravaggio. In the complex variety of collaborations between father and son in the second decade of the Seicento, such an inversion of the natural roles of father-master and son-pupil is very rare; it is precisely for this reason that the re-emergence of the bust is particularly significant. No less interesting is the subject of the work: a bust of Christ rooted in the purest Florentine tradition. The marble constitutes a fundamental link in the transmission from father to son of an iconographic model that Gian Lorenzo would cultivate until the end in the grand 'Salvator mundi ' from his last years, the original of which we recognize in the example at Norfolk, assigning the version at San Sebastiano fuori le Mura at Rome instead to Giuseppe Mazzuoli.