Leaf and stem essential oils of Harungana madagascariensis Lam. ex Poir, [an endangered medicinal Hypericaceae] were obtained in Nigeria by hydro-distillation using the all-glass Clevenger apparatus designed to British Pharmacopeia specifications. It gave good yields of 0.13and0.08 % respectively. The oils were analyzed using gas chromatography [GC], gas chromatography-mass spectrometry [GC-MS] in University of Botswana. Forty-nine compounds were identified in leaf oil, which account for 85.64 % of it; while fifteen identified compounds are responsible for 56.82 % of stem oil. Most abundant compounds in leaf oil are α-caryophyllene (33.41 %); β-caryophyllene (17.78 %) and 1-ethenyl-1-methyl-2,4-bis(1-methylethenyl)-[1S-(1α,2α,4α)]- cyclohexane (6.21 %). Dominant compounds in stem oil are α-caryophyllene (22.38 %); α-farnesene (13.90 %) andβ-caryophyllene (8.26 %). Leaf oil is dominated by unique classes of compounds (%): like the ubiquitous sesquiterpenes (56.53) and sesquiterpenoids (1.91);naphthalenes (13.33); unsaturated mostly diene hydrocarbons (7.04); aromatics (3.02); azulenes (1.36);alcohols (1.02); esters (0.89); sulfurates (0.19); ketones (0.18); alanine derivative (0.08); phenols (0.05) and squalene (0.04).Classes of compounds in stem oil are (%) the ubiquitous sesquiterpenes (45.62) and sesquiterpenoids (1.05); hydrocarbons (5.00); aromatics (2.21); azulenes (1.42); naphthalenes (1.32) and alcohols (0.20). Our results indicate that Harungana madagascariensis essential oils are terpenoidal, dominated by sesquiterpenes. This study revealed important compounds in the leaf and stem essential oils of Harungana madagascariensis, which have not been reported earlier in literature.