This study investigated the phytochemical characteristics, antibacterial activity, and synergistic potential of essential oils derived from Romanian lavender. Gas Chromatography–Mass Spectrometry (GC/MS) analysis revealed that linalool is the main compound in all lavender essential oils, with concentrations ranging from 29.410% to 35.769%. Linalyl acetate was found in similar concentrations to linalool. Other significant compounds included 1,8-cineole (8.50%), lavandulyl acetate (5.38%), trans-β-ocimene (6.90%), and camphor (7.7%). A 1,1-Diphenyl-2-Picrylhydrazyl (DPPH) test was used to assess antioxidant capacity, with substantial free-radical-scavenging activity shown in the IC₅₀ values determined. The antibacterial efficacy of the oils was higher against Gram-positive bacteria than Gram-negative bacteria, with variations in minimum inhibitory concentrations (MICs), the extent of inhibition, and evolution patterns. The study also explored the oils’ ability to enhance the efficacy of ampicillin, revealing synergistic interactions expressed as fractional inhibitory concentration indices. In silico protein–ligand docking studies used twenty-one compounds identified by GC-MS with bacterial protein targets, showing notable binding interactions with SasG (−6.3 kcal/mol to −4.6 kcal/mol) and KAS III (−6.2 kcal/mol to −4.9 kcal/mol). Overall, the results indicate that Romanian lavender essential oils possess potent antioxidant and antibacterial properties, and their synergistic interaction with ampicillin has potential for enhancing antibiotic therapies.