Investigation of bioactive compounds from the rhizomes of <i>Kaempferia elegans</i> led to the isolation and characterization of ten new diterpenoids, namely, five 12,13-<i>seco</i>-diterpenoids named elegansins A-E (<b>1</b>-<b>5</b>) and five new abietanes, elegansols A-E (<b>6</b>-<b>10</b>), together with seven known diterpenoids (<b>11</b>-<b>17</b>). The structure elucidation of the new compounds was achieved by HRESIMS, NMR, and ECD spectroscopic analysis. Compounds (<b>1</b>-<b>5</b>) are the first examples of 12,13-<i>seco</i>-diterpenoid-type compounds representing a decalin fused dihydropyran skeleton. Plausible biosynthetic pathways for compounds <b>1</b>-<b>5</b> are proposed. Aromatase inhibitory activities of all compounds were evaluated, and abieta-8,11,13-trien-11-ol (<b>16</b>) was found to be the most potent aromatase inhibitor with an IC<sub>50</sub> value of 3.7 μM.