Neem oil, extracted from the seeds of Azadirachta indica (family Meliaceae), is renowned for its wide range of bioactivities, including insecticidal, antibacterial, antifungal, antiviral, antioxidant, and anti-inflammatory properties. However, its poor water solubility, susceptibility to oxidation, and instability under light and temperature restrict its direct use in pharmaceutical, agricultural, and cosmetic applications. Nanoemulsion technology has emerged as an effective strategy to overcome these challenges by encapsulating neem oil within nanosized droplets (typically 20–200 nm), thereby enhancing its solubility, bioavailability, stability, and controlled release. Neem oil Nanoemulsion (NEs) are generally prepared using high-energy (ultrasonication, high-pressure homogenization) or low-energy (phase inversion, spontaneous emulsification) methods with biocompatible surfactants and co-surfactants. Numerous studies have reported improved larvicidal, pesticidal, and antimicrobial activities of neem oil NEs compared to bulk formulations, owing to increased surface area, better wetting, and deeper penetration into biological membranes. Furthermore, recent advances focus on green surfactants, solid nanoemulsion gels, and polymer-based delivery systems for sustained efficacy and reduced toxicity. This review critically discusses the formulation strategies, characterization techniques, biological applications, and future prospects of neem oil nanoemulsions, highlighting their potential as eco-friendly and multifunctional nanocarriers for sustainable agriculture and biomedicine.