A nanoparticle is the simplest structural component due to its nanometer-sized diameter. Nanoparticles are typically atoms or molecules that generate a radius (or diameter) of less than 100 nm when bonded collectively. The latest developments in nanotechnology provide a wide range of methods for studying and monitoring various medical and biological processes at the nanoscale. Nanoparticles can help diagnose and treat diseases, such as cancer, by carrying drugs directly to cancer cells. They can also be used to detect disease biomarkers in the body, helping to provide early diagnosis. It is likely that the data will have a positive effect on biology and medicine. It is plausible that nanoparticles could be used in theranostic applications and targeted drug delivery. This could significantly improve patient outcomes and reduce the amount of time, effort, and money needed to diagnose and treat diseases. It could also reduce the side effects of treatments, providing more precise and effective treatments. Nanoparticles for biomedical applications include polymeric and metal nanoparticles; liposomes and micelles; dendrimers and quantum dots; etc. Among the nanoparticles, gold nanoparticles have emerged as a promising platform for drug delivery applications. Gold nanoparticles are highly advantageous for drug delivery applications due to their excellent biocompatibility, stability, and tunable physical and chemical properties. The present review provides an in-depth discussion of the various approaches to gold nanoparticle synthesis and drug delivery applications.