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Non-timber forest products (NTFPs) play a fundamental role in food security, public health, and the socio-economic equilibrium of rural and peri-urban households in Central Africa. Among these resources, Gnetum africanum Welw. and Gnetum buchholzianum Engl. (locally known in Gabon as Nkumu) stand out as multi-purpose lianas whose edible leaves are highly valued for their nutritional, medicinal, and economic qualities. This integrative review synthesizes multidisciplinary scientific evidence and institutional reports concerning Gnetum spp. in Gabon and the wider Congo Basin. Grounded in a methodical literature screening process inspired by the PRISMA 2020 framework (covering the period 1990–2025), this study analyzes: (1) the botanical, ecological, and geographical distribution of the two species; (2) their detailed nutritional composition, bioactive phytochemicals, and anti- nutritional factors; (3) the impact of traditional and thermal processing methods on nutrient retention and digestibility; (4) traditional ethnobotanical uses and emerging pharmacological applications; (5) the structure, actor network, and economic dynamics of the supply chain; and (6) their contribution to the United Nations Sustainable Development Goals (SDGs). The findings demonstrate that Gnetum spp. leaves represent a rich source of plant proteins, dietary fibers, essential minerals (calcium, iron, potassium, magnesium), and bio-active secondary metabolites (polynols, flavonoids, stilbenes such as gnetol and gnetins). Traditional processing techniques (blanching, steaming, boiling) significantly reduce anti-nutritional compounds (oxalates, phytates, tannins) and enhance nutrient bioavailability, although prolonged heat treatment can deplete thermolabile vitamins. Economically, the Gnetum supply chain constitutes a vital source of income and a key vector for women's empowerment in Gabon. However, the sector faces severe sustainability bottlenecks, including total reliance on wild harvesting, destructive collection practices, habitat loss, post-harvest perishability, lack of quality standardization, and slow progress in domestication and agroforestry integration. To transition from informal exploitation to a sustainable and bioeconomic value chain, this paper proposes an integrated policy framework prioritizing participatory domestication, sustainable harvesting guidelines, post-harvest technological innovation, gender- inclusive financing, and institutional recognition of Gnetum spp. within national food security and forestry strategies.