Plant terpenoids are a vital source of natural products, yet their discovery is often hindered by low abundance or cryptic expression. The integration of genome mining and synthetic biology has emerged as a transformative solution, enabling systematic discovery and characterization of novel terpenoid scaffolds across all major terpenoid classes, including triterpenes, sesterterpenes, diterpenes, and sesquiterpenes. This review highlights key advances achieved through genome-wide functional characterization of terpene synthases, combinatorial biosynthesis approaches, and scalable production systems for bioactivity evaluation. These integrated strategies have proven particularly valuable for uncovering hidden terpenoid diversity and studying naturally rare terpenoids in plants, significantly expanding the chemical space available for pharmaceutical development and drug discovery.