Graphene, a single-layer allotrope of carbon, has attracted considerable attention in modern materials research owing to its exceptional electrical, thermal, optical, and mechanical properties. Among the various production routes, chemical reduction of graphene oxide (GO) is widely used; however, this method often involves hazardous reagents and raises environmental concerns. Although green synthesis approaches employing terrestrial plant extracts have been extensively reported, the potential of marine resources for graphene production remains largely unexplored. In this context, mangrove plants have recently gained interest as sustainable bio-resources due to their adaptation to extreme environments and their rich content of bioactive secondary metabolites. The present study aimed to develop an eco-friendly route for graphene synthesis by reducing graphene oxide using an aqueous leaf extract of the mangrove Avicennia marina. Graphene oxide was first synthesized from flake graphite using a modified Hummers’ method. The reduction process was then carried out using the A. marina leaf extract as a natural reducing and stabilizing agent. The resulting graphene was characterized using Raman spectroscopy, scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy. The results confirmed that A. marina leaf extract effectively reduced graphene oxide to graphene, likely due to the presence of polyphenols and other bioactive compounds. The spectroscopic and microscopic characteristics of the synthesized graphene were consistent with those reported in comparable studies, supporting the reliability of the proposed method. Overall, the findings demonstrate that mangrove leaf extract represents an effective, low-cost, and environmentally benign alternative to conventional chemical reductants for graphene production. This green synthesis approach offers a promising pathway for sustainable nanomaterial fabrication and highlights the underexplored potential of marine ecosystems, particularly mangroves, in advanced nanotechnology applications.