Over the past decades, metal nanoclusters have emerged as a novel class of highly attractive materials, owing to their atomic-level precision, complete homogeneity, and intriguing properties such as luminescence and catalytic activity. Typically, a metal nanocluster consists of a metal core surrounded by surface ligands. While the metal core plays a crucial role, it is increasingly recognized that surface ligands are far more than mere stabilizing agents. Compared to classical organic ligands such as thiolates and phosphines, oxygen (O) donors—including carboxylates, sulfonates, phosphinates, and phosphonates—have long been known but remain underestimated. Notably, O donors exhibit diverse coordination modes, making them particularly promising candidates for generating novel architectures. Moreover, O donors are highly effective in introducing chirality, luminescence, and other functionalities into metal nanoclusters. Many of these donors are also inexpensive, readily available, stable under ambient conditions, and easy to handle. In this review, we systematically summarize the development of O-donor protection in atomically precise cionage metal nanoclusters, with a particular emphasis on the structures of surface motifs associated with O donors. We also briefly survey the reported properties of clusters featuring O-donor protection. We hope this review will draw greater attention to O donors as ligands for nanoclusters, given their promising potential in generating novel structures and properties, particularly in coinage-metal nanoclusters.