Aims: The objective of this work is to determine the chemical composition and in vitro evaluation of the antibacterial activities of essential oils of four species of aromatic plants of Gabonese origin obtained by hydrodistillation. Methods: All the samples were examined by chromatographic analyzes and by GC / MS coupling. Antimicrobial activity was assessed by diffusion and microdilution methods. Results: The most common compounds found in essential oils were terpene hydrocarbons and oxygenates. The major constituents are β-phellandrene (56.3%), β-pinene (11%) and myrcene (10.4%). The three bacterial strains used are sensitive to essential oils. However, some essential oils stood out with greater spectra of action compared to others, such as Maranthes gabunensis and Mammea africana which showed activity against all strains. The inhibition parameters (MIC and CMB) are between 0.78 and 25 mg / mL. Some oils have shown bacteriostatic and / or bactericidal activity on the targeted strains. Conclusion: The essential oils studied present a diversity of chemical compositions and good antibacterial activities.