The Lamiaceae family is among the largest plant families, including more than 230 genera and 7,000 species. Many members of this family are well known for their aromatic and medicinal properties, attributed to their rich content of specialized metabolites. In Greece, the genera Sideritis, Stachys, and Salvia hold particular importance due to their traditional uses and their value as sources of bioactive compounds. This study aimed to investigate the phytochemical composition of selected Greek species belonging to these genera. Plant materials were extracted, and their chemical profiles were analyzed through several analytical techniques. The results revealed a high diversity of polyphenolic compounds, including mainly flavone 7-O-allosylglucosides and phenylethanoid glycosides in Sideritis and Stachys species, while flavone glycosides and depsides are present in Salvia species. Overall, the studied Greek species represent valuable sources of polyphenolic constituents with promising pharmacological activities and potential applications in pharmaceuticals, nutraceuticals, and cosmetic formulations.