WORD COUNT OF THE ARTICLE = 4744+183+19 = 4946 words Conspectus Sulfur-rich metalloproteins and metalloenzymes, containing strongly covalent metal-thiolate (cysteinate) or metal-sulfide bonds in their active site, are ubiquitous in nature. The metal-sulfur motif is a highly versatile tool involved in various biological processes: (i) metal storage, transport and detoxification; (ii) electron transfer; (iii) activation of the sulfur atom to promote different types of S-based reactions including S-alkylation, S-oxygenation, S-nitrosylation, disulfide or thiyl radicals formation; (iv) activation of small earth-abundant molecules (such as water, dioxygen, superoxide radical anion, carbon oxides, nitrous oxide and dinitrogen). This Account describes our investigations carried out during the last ten years on bio-inspired and biomimetic low-nuclearity complexes containing metal-thiolate bonds. The general objective of these structural, spectroscopic, electrochemical and catalytic studies was to determine structure-properties-function correlations useful to (i) understand the peculiar features or the mechanism of the mimicked natural systems and/or (ii) reproduce enzymatic reactivities for specific catalytic applications. By employing a unique highly preorganized N2S2-donor ligand with two thiolate functions, in combination with different first-row transition metals (Mn, Fe, Co, Ni, Cu, Zn, V), we got access to a series of bio-inspired sulfur-rich complexes displaying a widespread spectrum of structures, properties and functions. We isolated a dicopper(I) complex that, for the first-time, mimicked concomitantly the key structural, spectroscopic and redox features of the biological CuA center, a highly efficient electron transfer agent involved in the respiratory enzyme cytochrome c oxidase. In the field of sulfur activation, we explored (i) sulfur methylation promoted by a Zn-dithiolate complex that mimics Zn-dependent thiolate alkylation proteins and shows different selectivity compared to the Ni and Co congeners, and (ii) a series of Co, Fe, Mn complexes as the first copper-free systems able to promote thiolate/disulfide interconversion mediated by (de)coordination of halides. Concerning metal-centered reactivity,