van Tetrode, known in Italy as Guglielmo Fiammingo (before c. 1530, Delft — after 1587),[1] was a sixteenth-century sculptor of Dutch origin who served as a pupil of Benvenuto Cellini in Florence.

[4] In Rome he worked under the direction of Guglielmo della Porta, restoring antiquities for the Cortile del Belvedere and other Vatican projects.

On his return to Florence in 1562, Guglielmo reminded Cosimo of his former work on the Ganymede,[5] The work in question, executed under Cellini's direction and commonly attributed to him, shows uncommonly refined cutting; Anthony Radcliffe remarked "it must be asked to what extent the beautiful statue now in the Bargello is the product of the technical skill of Willem van Tetrode".

[6] Giorgio Vasari records a writing cabinet adorned with bronze replicas of the antique Dioscuri, the Apollo Belvedere, the Farnese Hercules and the Venus de' Medici and at least sixteen other statuettes by Fiammingo; it was commissioned by Nicolò Orsini, conte di Pitigliano and completed in 1559, intended as a diplomatic gift for Philip II of Spain.

[7] Three of the bronze fauns on Bartolommeo Ammanati's Fountain of Neptune that were long attributed to Guglielmo Fiammingo cannot be his, since their facture is documented as being begun in March 1571 and finished in June 1575, by which time, Anthony Radcliffe has pointed out,[8] van Tetrode was back in Delft by 1566–67; there in 1568 he signed a contract for the new high altar in the Oude Kerk, which he finished in 1573.