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We developed an instantaneously usable screen-printed silver/silver sulfate (Ag/Ag2SO4) reference electrode with long-term stability. The reference electrode was composed of a Ag layer, a Ag/Ag2SO4 layer, an inner electrolyte layer, and a liquid junction layer printed successively on a polyimide substrate. The liquid junction and inner electrolyte layers were prepared using a silica gel–poly(vinylidene difluoride) ink. The open-circuit potentials in different electrolyte solutions were compared to that measured using a commercial reference electrode. The fabricated reference electrode stabilized the potential shift within 30 min and gave 437 mV vs. saturated KCl/Ag/AgCl measured in a 1 M KNO3 solution; the result was in good agreement with the theoretical value. Furthermore, the fabricated reference electrode remained stable for 20 days. This Ag/Ag2SO4 reference electrode showed potential for application in measurement systems where contamination by chloride ions is not desirable. Keywords: Reference electrode, Silver/silver sulfate, Screen-printing, Long-term stable, Instantaneously usable