<p>Essential oils from Eucalyptus species have broad use in various sectors of health, agriculture, and other industries. This study aimed to identify the predominant constituents in essential oils extracted from leaves of ten eucalyptus species (<i>Eucalyptus</i> and <i>Corymbia</i> genus, Myrtaceae family). Leaves were collected from cultivated in the field (adult plants) and greenhouse (young plants) and assessed whether these conditions affect the oil characteristics. Essential oils were extracted by hydrodistillation and their composition was obtained using gas chromatography-mass spectrometry (GC-MS). The results showed a large variation among species and samples from the field and greenhouse. The results were compared with the literature and confirmed how variable eucalyptus essential oil can be. The variability observed among the species studied is substantial, and this pattern persists when compared with previous studies. However, this comparison does not account for other influencing factors such as genetic material, plant age, and additional variables that may also affect both the quantity and diversity of the constituents found. Among the field-grown plants, the most abundant active compound was eucalyptol and α-pinene, while in the greenhouse-grown plants, globulol predominated. In addition, globulol and aromadendrene were more frequently found in the greenhouse conditions, and α-pinene and eucalyptol in field conditions. Other compounds were exclusive to a single species and a single condition, such as bulnesol, guaiol, and β-cadinene in <i>E. henryi</i> grown in the greenhouse.</p>