ABSTRACT The development of reliable, eco-friendly processes for the production and application of nanoparticles in biology are important facts in present scenario of nanotechnology. Now a days nano-metal particles especially gold have drawn the attention of scientist because of their extensive application in the development of new technologies in the areas of medicine, biotechnology etc. One approach that shows immense potential is based on the biosynthesis of nanoparticles using medicinal plants. Withania somnifera also known as ashwagandha, Indian ginseng and winter cherry has plays a vital role in the ayurvedic and indigenous medical systems for over 3000 years. Withania somnifera, or Ashwagandha, is native to drier parts of India and the world. The plants contain the alkaloids withanine and somniferine, which are used therapeutically. The roots are the main portion of the plant used therapeutically. As part of our investigation, we have observed that aqueous gold chloride when exposed to the plant extract is reduced in solution, thereby leading to the formation of an extremely stable gold nanoparticle. It is believed that the reduction of the metal ions occurs due to the presence of alkaloids and terpenoids of the plant extract. Appearance of the ruby red color confirms the gold nanoparticle synthesis and this was confirmed by UV-Visible spectrophotometry analysis at 540 nm. The biosynthesized gold nanoparticles were characterized for its shape of the crystal by Fourier Transform Infra red spectroscopy (FTIR), X-ray Diffractometry (XRD) and High resolution Transmission Electron Microscopy (HRTEM). Further more the antibacterial activity of the synthesized nanoparticles were also carried out against Staphylococcus aureus (I-332), Pseudomonas aeruginosa (I-326), Proteus mirabilis (I-278) and Staphylococcus species (I-328, NFGNB (I-332). This preliminary study paves a greener technology for synthesis of gold nanoparticles.