This work presents a highly sensitive and selective electrochemical sensor for glutathione (GSH) detection using a glassy carbon (GC) electrode modified with zinc oxide quantum dots-reduced graphene oxide nanocomposites (ZnO QDs-rGO NCs). The ZnO QDs (diameters about similar to 2 to 8 nm) were synthesized and successfully anchored onto the surface of reduced graphene oxide (rGO). The resulting nanocomposites were then characterized using various spectroscopic and microscopic techniques. The wurtzite crystal structure of ZnO and anchored onto the rGO surface were confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The synergistic interaction between ZnO QDs with rGO provides a large surface area, high conductivity, and efficient transfer of electrons, resulting in improved electrocatalytic activity for GSH oxidation. The ZnO QDs-rGO/GC electrode exhibits exceptional performance with a wide linear range (0.01-10 mu M), high sensitivity (3.66 mu A mu M-1),- 1 ), and excellent selectivity for GSH. The sensor demonstrates good analytical stability, characterized by high reproducibility (%RSD = 2.90%) and repeatability (%RSD = 1.49%), and maintains its performance in the presence of common biological interferences. The applicability of the sensor was validated through successful GSH detection in complex matrices like human blood and pharmaceutical capsules, achieving recovery rates of 98.1-102.0% with excellent reliability. C1 [Vinoth, Victor; Pugazhenthiran, Nalandhiran] Univ Tecn Federico Santa Maria, Dept Quim, Lab Fotoquim & Fotofis, Ave Espana 1680, Valparaiso, Chile. [Subramaniyam, Gowrishankar; Manidurai, Paulraj] Univ Concepcion, Fac Phys Sci & Math, Dept Phys, POB 160 C, Concepcion, Chile. [Kaimal, Reshma; Anandan, Sambandam] Natl Inst Technol, Dept Chem, Nanomat & Solar Energy Convers Lab, Tiruchirappalli 620015, India. [Kaimal, Reshma] Harbin Inst Technol Shenzhen, Sch Sci, Shenzhen 518055, Peoples R China. [Shanmugaraj, Krishnamoorthy] Univ Tarapaca, Fac Ciencias, Dept Quim, Avda Gen Velasquez 1775, Arica, Chile. [Raj, Balasubramaniam Gnana Sundara] Velammal Coll Engn & Technol, Dept Chem, Madurai 625009, Tamil Nadu, India. [Thirumurugan, Arun] Univ Atacama, Sede Vallenar, Ave Costanera 105, Vallenar 1612178, Chile. [Thandapani, Prabhakaran] VIT AP Univ, Sch Adv Sci, Dept Phys, Amaravati 522237, Andhra Pradesh, India. C3 Universidad Tecnica Federico Santa Maria; Universidad de Concepcion; National Institute of Technology (NIT System); National Institute of Technology Tiruchirappalli; Harbin Institute of Technology; Universidad de Tarapaca; Universidad de Atacama; VIT-AP University