This paper examines the role and importance of Amphitrite in Catullus c. 64, the epyllion on the wedding of Peleus and Thetis. Catullus intends to conjure up Amphitrite's rich mythological background for the needs of his poem. Amphitrite's story contains thematic elements that recur in both narratives of c. 64, namely the main story of Peleus and Thetis, and the embedded story of Theseus and Ariadne. At the same time Amphitrite's meaningful presence in the prologue of c. 64 is a pointer to Bacchylides' Dithyramb 17, which treats Theseus' outbound journey to Crete and the test of his divine paternity, imposed by Minos. The several points of contact between B. Dith. 17 and Catul. c. 64 show that this Greek poem is an important subtext for c. 64, which has gone unnoticed so far.