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Sea cucumbers are the most prevalent marine invertebrates in Indonesian waters, yet little research has been conducted on the bioactive substances found in the sea cucumbers harvested from these waters. To investigate the potential use of sea cucumber extracts and fractions such as antibacterial and antioxidant agents, five sea cucumber species were harvested from Lampung waters in Indonesia. The extraction process used the maceration method with methanol solvent, while fractionation was carried out with n-hexane, ethyl acetate, and butanol solvents. The antibacterial activity was evaluated using the agar diffusion method, and the antioxidant activity was assessed using the ABTS (2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) method. The GC–MS method was used to identify the compounds in the methanol extract and butanol fraction of Holothuria lessoni. The results showed that only the n-hexane fraction of Stichopus quadrifasciatus and the methanol extract of H. lessoni had antibacterial activity against Propionibacterium acnes, while the methanol extract of H. lessoni and the ethyl acetate fraction of H. leucospilota showed activity against Staphylococcus aureus. The n-hexane fraction of S. quadrifasciatus and the methanol extract of H. lessoni and Bohadschia marmorata recorded activity against Staphylococcus epidermidis. Among the tested extracts, Holothuria leucospilota showed the highest antioxidant activity in methanol extracts, with an IC50 value of 155.07 ​± ​3.05 ​μg/mL, followed by H. lessoni (163.83 ​± ​4.46 ​μg/mL), Stichopus vastus (209.45 ​± ​2.40 ​μg/mL), S. quadrifasciatus (245.85 ​± ​34.97 ​μg/mL), and B. marmorata (382.86 ​± ​45.37 ​μg/mL), respectively. Cyclononasiloxane, octadecamethyl- (C18H54O9Si9), cyclohexasiloxane, dodecamethyl (C12H36O6Si), and cyclooctasiloxane, hexadecamethyl- (C16H48O8Si8) were identified as the main compounds in the tested samples using GC–MS analysis. In conclusion, H. lessoni is a valuable source of natural antibacterial and antioxidant agents. [ABSTRACT FROM AUTHOR]