Cancer continues to pose a major global health burden, and despite the widespread clinical use of platinum-based chemotherapeutic agents such as cisplatin, their application is often limited by significant toxicity and poor selectivity toward cancer cells. These drawbacks have driven growing interest in alternative metal-based therapeutics. In particular, gold complexes have attracted attention due to their unique modes of action, which differ fundamentally from those of platinum drugs and may offer opportunities to overcome resistance and improve therapeutic outcomes. In this study, we report the synthesis and biological evaluation of a series of novel gold-phosphine complexes designed to explore structure-activity relationships and assess their anticancer potential. The complexes were synthesized using standard coordination chemistry approaches and were fully characterized by spectroscopic techniques to confirm their composition and stability. Their biological activity was evaluated through in vitro cytotoxicity assays against selected cancer cell lines, with cisplatin used as a reference compound. In addition, preliminary mechanistic studies were carried out to gain insight into their possible modes of action. The results reveal that several of the gold-phosphine complexes exhibit cytotoxic activity comparable to, and in some cases exceeding, that of cisplatin. Variations in the phosphine ligand framework were found to influence biological activity, suggesting a clear structure-activity relationship within this series. Overall, these findings highlight the potential of gold-phosphine complexes as promising anticancer candidates and provide a useful foundation for the further development and optimization of gold-based chemotherapeutic agents