Compositional Characteristics of Macadamia Nuts and Oils from Major Growing Regions in China: A Static Evaluation

China’s macadamia industry has expanded remarkably; however, a comprehensive understanding of the interaction between cultivar and geographical origin in shaping oil quality remains limited. This gap constrains the development of high-value products. To address this, we conducted a systematic and comparative evaluation of macadamia nuts and their pressed oils from 15 representative cultivars across Yunnan, Guangxi, and Guangdong. Our analysis encompassed physicochemical properties, fatty acid profiles, key minor components (tocopherols, squalene, and polyphenols), and antioxidant activities. Oleic acid (56.66–62.75%) and palmitoleic acid (12.24–18.73%) were the dominant fatty acids, with Yunnan oils exhibiting the highest unsaturated fatty acid content (80.86%). Multivariate analyses revealed that geographical origin was a more dominant factor than cultivar in shaping the overall compositional profile, particularly for the minor bioactive components. A strong positive correlation was established between antioxidant capacity and the contents of polyphenols, squalene, and tocopherols. The Guangxi A4 cultivar emerged as the premier material due to its superior fatty acid profile, high bioactive content (squalene: 329.01 mg/kg; tocopherols: 64.10 mg/kg), and potent antioxidant capacity. Our findings provide a scientific foundation for the selective breeding and origin-based standardization of premium macadamia oils in China.