| Summary: | <i>Alpinia galanga</i> is widely cultivated for its essential oil (EO), which has been used in cosmetics and perfumes. Previous studies of <i>A. galanga</i> focussed mostly on the rhizome but seldom on the flower. Therefore, this study was designed to identify the chemical composition of <i>A. galanga</i> flower EO and firstly estimate its antioxidant, antibacterial, enzyme inhibitory, and anticancer activities. According to the results of the gas chromatography with flame ionization or mass selective detection (GC-FID/MS) analysis, the most abundant component of the EO was farnesene (64.3%), followed by farnesyl acetate (3.6%), aceteugenol (3.2%), eugenol (3.1%), <i>E</i>-nerolidol (2.9%), decyl acetate (2.4%), octyl acetate (2.0%), sesquirosefuran (1.9%), (<i>E</i>)-<i>β</i>-farnesene (1.7%), and germacrene D (1.5%). For the bioactivities, the EO exhibited moderate DPPH and ABTS radical scavenging effects with IC<sub>50</sub> values of 138.62 ± 3.07 μg/mL and 40.48 ± 0.49 μg/mL, respectively. Moreover, the EO showed strong-to-moderate antibacterial activities with various diameter of inhibition zone (DIZ) (8.79–14.32 mm), minimal inhibitory concentration (MIC) (3.13–6.25 mg/mL), and minimal bactericidal concentration (MBC) (6.25–12.50 mg/mL) values against <i>Staphylococcus aureus</i>, <i>Bacillus subtilis</i>, <i>Enterococcus faecalis</i>, <i>Pseudomonas aeruginosa</i>, <i>Escherichia coli</i>, and <i>Proteus vulgaris</i>. Interestingly, the EO possessed remarkable α-glucosidase inhibition (IC<sub>50</sub> = 0.16 ± 0.03 mg/mL), which was equivalent to that of the positive control acarbose (IC<sub>50</sub> = 0.15 ± 0.01 mg/mL) (<i>p</i> > 0.05). It showed moderate tyrosinase inhibition (IC<sub>50</sub> = 0.62 ± 0.09 mg/mL) and weak inhibitory activity on acetylcholinesterase (AChE) (IC<sub>50</sub> = 2.49 ± 0.24 mg/mL) and butyrylcholinesterase (BChE) (IC<sub>50</sub> = 10.14 ± 0.59 mg/mL). Furthermore, the EO exhibited considerable selective cytotoxicity to K562 cells (IC<sub>50</sub> = 41.55 ± 2.28 μg/mL) and lower cytotoxicity to non-cancerous L929 cells (IC<sub>50</sub> = 120.54 ± 8.37 μg/mL), and it induced K562 cell apoptosis in a dose-dependent manner. Hence, <i>A. galanga</i> flower EO could be regarded as a bioactive natural product with great application potential in the pharmaceutical field.
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