Natural products are valuable sources of bioactive compounds with therapeutic potential. This study investigated the chemical composition, antioxidant properties, and enzyme inhibitory activities of the methanol extract from Sideritis montana L. subsp. montana L. obtained via ultrasound-assisted extraction. The extraction yielded 5.37%, with a total phenolic content of 63.27 mg GAEs/g extract and a total flavonoid content of 58.32 mg REs/g extract. Chlorogenic acid (563 µg/g extract), luteolin 7-glucoside (513 µg/g extract), and hyperoside (511 µg/g extract) were the most abundant phenolics. Moderate levels of luteolin and hydroxybenzoic acids were also identified. Antioxidant activity was most pronounced in the phosphomolybdenum assay (428.52 mg TEs/g extract), followed by the CUPRAC (217.40 mg TEs/g extract) and FRAP (171.33 mg TEs/g extract) assays, demonstrating strong reducing power. Radical scavenging assays (DPPH: 122.76 mg TEs/g, ABTS: 140.41 mg TEs/g) showed moderate efficacy, while ferrous ion chelation was weak (6.62 mg EDTAEs/g extract). Enzyme inhibition assays indicated potent α-glucosidase (753.81 mg ACEs/g extract) and α-amylase (274.95 mg ACEs/g extract) inhibition, suggesting antidiabetic potential. Tyrosinase inhibition (68.56 mg KAEs/g extract) points to possible dermatological applications, though acetylcholinesterase (2.08 mg GALAEs/g extract) and butyrylcholinesterase (0.45 mg GALAEs/g extract) inhibition was minimal. The results emphasize the bioactive potential of S. montana subsp. montana. Future studies should explore its bioactivity in vivo and identify synergistic effects among its phenolic compounds to further validate its therapeutic applications.