Skin ageing, driven predominantly by oxidative stress from reactive oxygen species (ROS) induced by environmental factors like ultraviolet A (UVA) radiation, accounts for approximately 80% of extrinsic skin damage. L-glutathione (GSH), a potent antioxidant, holds promise in combating UVA-induced oxidative stress. However, its instability and limited penetration through the stratum corneum hinder its topical application. This study introduces a novel solid lipid nanoparticle (SLN)-enriched hydrogel designed to enhance GSH stability, skin penetration, and sustained release for anti-ageing applications. GSH-loaded SLNs were prepared via a double-emulsion technique and optimized using factorial design. These SLNs were incorporated into 1-3% (/) Carbopol hydrogels to produce a semi-solid formulation. The hydrogel's characteristics, including morphology, mechanical and rheological properties, drug release, stability, antioxidant activity, cytotoxicity, and skin penetration, were evaluated. SEM and FTIR confirmed the uniform dispersion of SLNs within the hydrogel. The formulation exhibited desirable properties, including gel strength (5.1 ± 0.5 g), spreadability (33.6 ± 1.9 g·s), pseudoplasticity, and elasticity. In vitro studies revealed a biphasic GSH release profile, with sustained release over 72 h and over 70% cumulative release. The hydrogel significantly improved antioxidant capacity, protecting human fibroblasts from UVA-induced oxidative stress and enhancing cell viability. Stability studies indicated that 4 °C was optimal for storage over three months. Notably, the hydrogel enhanced GSH penetration through the stratum corneum by 3.7-fold. This SLN-enriched hydrogel effectively improves GSH topical delivery and antioxidant efficacy, providing a promising platform for anti-ageing and other bioactive compounds with similar delivery challenges.