Developing a facile and green approach to synthesize gold nanoparticles (AuNPs) with high catalytic activities for the reduction of toxic nitrophenols to beneficial aminophenols is of tremendous environmental and industrial relevance. The present study reports an environmentally benign synthesis of AuNPs using aqueous extract of seaweed Lobophora variegata as a potential bioreductant. The signatory pinkish red color and a surface Plasmon resonance peak at 530 nm in the UV-Visible spectrum confirmed the formation of AuNPs. TEM images revealed that the biosynthesised AuNPs were spherical in shape with an average size of 11.69 + 2.38 nm. The high crystallinity of the biogenic AuNPs is confirmed from the clear lattice fringes in the High resolution TEM images, bright circular rings in SAED pattern and Bragg's reflections of (111), (200), and (220) in XRD pattern. FTIR spectra revealed the role of bioactive metabolites in stabilizing the nanoparticles. The report emphasizes the spectroscopic investigation on the efficacy of the biosynthesized AuNPs as excellent catalyst in the reduction of anthropogenic organic pollutants, 4-nitrophenol (4NP), 3-nitrophenol (3NP), and 2-nitrophenol (2NP) to the corresponding aminophenols using NaBH4, which followed a pseudo-first-order kinetics with rate constants in the order k(2NP) > k(4NP) > k(3NP).