The green synthesis of nanoparticles using environmentally conscious procedures is vital due to its eco-friendly characteristics, diminished energy requirements, and the avoidance of perilous chemicals. Manganese di oxide (MnO₂) nanoparticles have widespread applications in diverse fields such as electronics, catalysis, environmental remediation, drug delivery, ceramics, material science, and sensors. Typically, MnO₂ nanoparticles are produced through physical, chemical, and biological methodologies. A freshly extracted botanical solution from Alternanthera sessilis is employed in nanoparticle synthesis owing to its economical nature and easy accessibility, serving as both a reducing and stabilizing agent. The biosynthesized MnO₂ nanoparticles underwent comprehensive characterization through distinct techniques, including X-ray Diffraction (XRD) studies, Fourier Transform Infrared Spectroscopy (FTIR) studies, Ultra Violet Visible (UV) Spectroscopy, and Transmission Electron Microscopy (TEM) studies. The XRD analysis facilitated the identification of crystal phases in the Manganese di oxide (MnO₂) nanoparticles. Additionally, the Debye--Scherrer equation was utilized for determining the crystallite size of the nanoparticles based on X-ray diffraction findings. Diverse functional groups present in Manganese di oxide (MnO₂) nanoparticles were confirmed through Fourier Transform Infrared Spectroscopy results, while Ultra Violet Visible absorption spectra were indicative of the energy band-gap value of the MnO₂ nanoparticles, and Transmission Electron Microscopy observations depicted the spherical morphology of the synthesized nanoparticles.