<p>A comprehensive investigation of catalytic phenomena using a catalyst with well-defined structures represents a fundamental research strategy in catalytic chemistry. Carbon-based single-atom catalysts, particularly single-atom metal nitrogen-doped carbon (SA-M-NC) materials, have emerged as ideal model systems for mechanistic studies due to their isolated, adjustable, and uniform active sites, along with their outstanding performances across a wide range of catalytic reactions. Given that all metal atoms in SA-M-NC are immobilized and coordinatively saturated, even minor modifications to the coordination environment can lead to significant changes in catalytic behavior. Consequently, structure-activity relationship studies centered on the “coordination environment-performance” correlation have become a central focus in this field. This review summarizes the prevailing configurations dominated by planar four-coordination geometries, as well as a variety of emerging coordination structures, and offers perspectives on the future design and development of advanced coordination architectures in SA-M-NC materials.</p>