Gold nanoparticles (AuNPs)Gold nanoparticles (AuNPs) have emerged as a promising tool in neurological therapeuticsTherapeutics due to their unique properties and capabilities. These nanoscale particles, characterized by their size, shape, surface charge, and functionalization, exhibit the remarkable ability to cross the blood–brain barrierBlood-brain barrier (BBB)—a significant advantage in treating brainBrain diseases. AuNPsGold nanoparticles (AuNPs) have demonstrated potential in both the diagnosisDiagnosis and treatment of various neurological conditions, including neurodegenerative diseases such as Alzheimer’s disease (AD)Alzheimer’s disease (AD) and Parkinson’s diseases (PD)Parkinson’s diseases (PD), as well as gliomas, stroke, traumatic brain injury, and inflammatory conditions. In diagnostics, AuNPsGold nanoparticles (AuNPs) enhance imagingImaging techniques such as fluorescence, photoacoustic imaging, and contrast tomography. Their ability to bind specifically to pathological biomarkersBiomarkers enables improved detection and monitoring of diseases at early stages. For example, AuNPsGold nanoparticles (AuNPs) can be engineered to target proteins associated with AD and PD, increasing the sensitivity and accuracy of diagnostic tests. In therapeutic applications, AuNPsGold nanoparticles (AuNPs) serve as effective drug delivery systems. They can be designed to deliver therapeutic agents directly to the brain, improving treatment efficacy while minimizing side effects to surrounding healthy tissues. This targeted delivery is made possible by the functionalization of AuNPsGold nanoparticles (AuNPs) with specific molecules that interact with disease-related targets. Despite their promising prospects, the use of AuNPsGold nanoparticles (AuNPs) in medicine, particularly neurological diseasesNeurological diseases, presents significant challenges. Ensuring the safetySafety and biocompatibilityBiocompatibility of these nanoparticlesNanoparticles (NPs) is crucial, as their long-term effects on the central nervous systemNervous system require thorough investigation. Comprehensive preclinical and clinical studies are therefore essential to establish their efficacy and safetySafety for widespread clinical application. This chapter provides a detailed review of current research on AuNPsGold nanoparticles (AuNPs), with a focus on their applications in diagnosing and treating AD and PD. It highlights recent advancements in preclinical and clinical settings and discusses both the potential and limitations of AuNPsGold nanoparticles (AuNPs) in these critical areas of neurological research.