Gold nanoparticles (GNPs) have become essential in nanobiotechnology due to their unique physicochemical properties, including size-dependent optical properties, biocompatibility, and ease of functionalization. This review explores the synthesis, properties, and biosensing applications of GNPs, emphasizing their role in biosensors. GNPs are particularly valuable for biosensing due to their ability to exhibit surface plasmon resonance (SPR), which allows for sensitive detection without the need for labels. Their high surface area enables the attachment of numerous biomolecules, enhancing sensitivity and selectivity. The review discusses various synthesis techniques, including biological methods using plants, algae, fungi, and bacteria, which offer advantages over traditional chemical methods in terms of sustainability and environmental impact. GNPs are used in a wide range of biosensing applications, including diagnostics, environmental monitoring, and drug delivery. Their versatility makes them suitable for detecting various biomarkers, pathogens, and pollutants. In forensic science, GNPs are used for latent fingerprint detection and the identification of gunshot residue and drugs. In pollution detection, GNPs are employed to monitor heavy metals, volatile organic compounds, and microbial contamination in water and soil. The review highlights the importance of functionalizing GNPs to enhance their binding specificity and sensitivity, which is crucial for accurate biosensing. The potential of GNPs in biosensing is underscored by their ability to provide label-free detection, high sensitivity, and adaptability to various biological and environmental conditions. Continued research into GNPs is essential for advancing their applications in healthcare and environmental science.Gold nanoparticles (GNPs) have become essential in nanobiotechnology due to their unique physicochemical properties, including size-dependent optical properties, biocompatibility, and ease of functionalization. This review explores the synthesis, properties, and biosensing applications of GNPs, emphasizing their role in biosensors. GNPs are particularly valuable for biosensing due to their ability to exhibit surface plasmon resonance (SPR), which allows for sensitive detection without the need for labels. Their high surface area enables the attachment of numerous biomolecules, enhancing sensitivity and selectivity. The review discusses various synthesis techniques, including biological methods using plants, algae, fungi, and bacteria, which offer advantages over traditional chemical methods in terms of sustainability and environmental impact. GNPs are used in a wide range of biosensing applications, including diagnostics, environmental monitoring, and drug delivery. Their versatility makes them suitable for detecting various biomarkers, pathogens, and pollutants. In forensic science, GNPs are used for latent fingerprint detection and the identification of gunshot residue and drugs. In pollution detection, GNPs are employed to monitor heavy metals, volatile organic compounds, and microbial contamination in water and soil. The review highlights the importance of functionalizing GNPs to enhance their binding specificity and sensitivity, which is crucial for accurate biosensing. The potential of GNPs in biosensing is underscored by their ability to provide label-free detection, high sensitivity, and adaptability to various biological and environmental conditions. Continued research into GNPs is essential for advancing their applications in healthcare and environmental science.