This study investigates the chemistry and potential applications of oils extracted from nine underutilized Nigerian seeds for cosmetic, pharmaceutical, and food industries. Oils were obtained from Balanites aegyptiaca, Arachis hypogaea, Hyptis spicigera, Sesamum radiatum, Sesamum indicum, Swietenia macrophylla, Citrullus lanatus, and two Cucumeropsis mannii varieties using mechanical pressing, then analyzed by GC-MS and UV spectrophotometry. Five seeds—B. aegyptiaca, A. hypogaea, S. radiatum, S. indicum, and S. macrophylla—yielded 20.9–36.8% oil, indicating commercial viability. GC-MS revealed 9,12-Octadecadienoic acid (linoleic acid) as the most abundant component across all samples, while S. macrophylla oil contained n-hexadecanoic acid and cis-vaccenic acid as major constituents. All oils demonstrated adequate UV absorbance across UVC to UVA regions (200–420 nm). Notably, C. lanatus, H. spicigera, and S. macrophylla exhibited the highest UVA absorbance ranges of 1.394–1.718, 1.449–1.702, and 1.402–1.711, respectively. While all samples can protect skin from UV radiation, these three oils possess superior potential for use as sunscreens with high sun protection factor (SPF). Further studies on antimicrobial, cosmeceutical, and nutraceutical potentials of these oils are recommended.