In the course of studies of nitrogen metabolism in tobacco plants, a new amino acid was isolated from Nicotiana tabacum L. "Hicks". This paper reports the isolation and structure elucidation of the amino acid tentatively named "nicotianamine". Green tobacco leaves (70 Kg) were extracted with 70% aqueous MeOH, purified using charcoal, Dowex 50W-X4 resin chromatography, and cellulose column chromatography to yield pure compound (I). The compound has the molecular formula C₁₂H₂₃N₃O₇ (elementary analysis), [α]ᵈ = -60.5 (C=2.7, water), darkens above 240°C without melting, is labile to mineral acid, tests positive for α-amino acid, and overlaps with asparagine/glutamine in amino acid analyzer elution. Structural elucidation using NMR, mass spectrometry (methyl/ethyl esters), catalytic hydrogenation, deutero labeling, KMnO₄ oxidation, DNP derivative UV spectroscopy, double resonance experiments, and high-resolution mass spectrometry revealed nicotianamine exists as a monohydrate and has the structure 1-[3'-(γ-amino-α,δ-dicarboxypropylamino)-propyl]-azetidine-2-carboxylic acid.