Sustainable,　renewable　and　scalable　production　of　highly　pure　hydrogen　gas　through　hydrogen　evolution　reaction　(HER)　in　electrochemical　water　splitting　requires　efficient　and　stable　electrocatalysts.　Single　atom　catalysts　(SACs)　with　significant　merits　such　as　the　maximum　atom-utilization　efficiency,　unique　electronic　structure　and　fascinating　properties,　are　considered　as　promising　candidates　electrocatalysts　for　HER.　Based　on　this,　recent　developments　of　effective　synthetic　methodology　toward　SACs　are　summarized.　Subsequently,　the　synergistic　coupling　interaction　between　the　catalytic　activity　and　SACs　including　the　perspective　of　coordination　environment,　local　structural　identification　and　metal-support　interaction　are　highlighted.　Finally,　the　current　challenges　and　future　opportunities　are　briefly　addressed　to　improve　the　performance　of　single-atom　electrocatalysts　for　HER,　which　might　offer　some　insights　for　applications　in　hydrogen　production.