Atomically　dispersed,　non-noble-metal　catalysts　represent　promising　alternatives　to　costly　platinum-group　electrocatalysts,　yet　precise　control　over　metal　site　proximity　remains　challenging.　Herein,　we　report　the　synthesis　of　ultrathin　(∼1.5　nm)　N-doped　carbon　nanosheets　decorated　with　densely　packed　single-atom　copper　sites　(Cu　SAs/N-CS),　achieved　via　controlled　pyrolysis　of　a　Cu–1H-1,2,4-triazole　complex　precursor.　The　resulting　Cu　SAs/N-CS　exhibits　a　high　copper　loading　(3.17　wt　%)　with　a　remarkably　short　average　interatomic　distance　(∼3.1　Å)　between　adjacent　Cu　atoms.　Inspired　by　multicopper　oxidase　enzymes,　these　closely　spaced　Cu　active　sites　facilitate　efficient　four-electron　(4e–)　oxygen　reduction　reactions　(ORRs),　displaying　superior　catalytic　performance　and　long-term　stability　in　both　neutral　and　alkaline　media.　Specifically,　Cu　SAs/N-CS　achieves　impressive　half-wave　potentials　of　0.68　V　(neutral)　and　0.91　V　(alkaline)　vs　RHE,　rivaling　commercial　Pt/C　under　neutral　conditions　and　outperforming　it　in　alkaline　electrolytes.　Density　functional　theory　(DFT)　analyses　indicate　that　short-range　Cu　site　proximity　upshifts　the　d-band　center,　strengthens　O2adsorption,　and　significantly　lowers　the　activation　barrier　for　the　4e–ORR　pathway,　thus　elucidating　the　mechanism　behind　its　exceptional　catalytic　activity.　©　2025　American　Chemical　Society