This study explores the structural performance of reinforced concrete (RC) beams confined internally with uniaxial polyester geogrids as partial replacements for traditional stirrups. Nine RC beam specimens with varying stirrup spacings (150 mm, 200 mm, and 350 mm) and geogrid confinement layers (0, 1, and 2 layers) were subjected to four-point static bending. The double-layer geogrid-confined beams demonstrated a ductility factor enhancement of 374%, an increase in ultimate load of up to 36%, and an improvement in energy dissipation of more than five times when compared to control specimens. The confinement transformed failure modes from brittle shear to more desirable ductile flexural failure. Initial stiffness improved by up to 60% with geogrid confinement. An analytical shear model, incorporating a confinement reduction factor (ψ = 0.95), accurately predicted ultimate load with an average error of 6.2%, validating the model's applicability. These findings highlight the potential of geogrids as a cost-effective solution for improving the shear behaviour and ductility of RC beams, particularly in small-scale applications.