Objective: To synthesise and characterise Pennisetum purpureum zinc oxide nanoparticles from aqueous extracts of elephant grass (Pennisetum purpureum). Methodology: Zinc oxide nanoparticles were synthesised with aqueous extract of elephant grass (Pennisetum purpureum) and zinc acetate dihydrate. It was characterized by using various dispersion methods such as UV-visible spectrophotometry, Transmission Electron Microscopy (TEM), Fourier Transform Infrared (FTIR) Spectroscopy and X-ray diffraction (XRD) to determine the morphology, crystallographic structure, chemical composition, physical properties and crystalline size of the nanoparticles. Results: The results showed that Zinc oxide nanoparticles were synthesized and characterized using various dispersion methods. UV–Vis spectra showed typical absorption peaks around 370nm (Pennisetum purpureum). FTIR revealed the presence of biomolecules and functional groups (C-O, O-H, CH, C≡C, C=C, N-O) that performs various functions like stabilizers, capping and coating agents in nanoparticle synthesis. XRD revealed the crystallographic structure, chemical composition, physical properties and crystalline size of the nanoparticles. The average crystalline size of zinc oxide nanoparticles was calculated using Debye–Scherer equation and the average size was 23.37nm. Conclusion: In this study, simple and green method for the synthesis of zinc oxide nanoparticles using aqueous extract of elephant grass (Pennisetum purpureum) and characterization using various dispersion methods was described. The formation of zinc oxide nanoparticle was confirmed by UV-Visible spectroscopy. The FTIR spectrum showed that the phytochemicals found in the plant extract was incorporated into the zinc oxide nanoparticle as capping and stabilizing agents. XRD results revealed the average size of 23.37nm (Pennisetum purpureum ZnO) and Transmission Electron microscopy (TEM) confirmed the morphology to be spherical.