Seven previously undescribed compounds were isolated from the endophytic fungus <i>Annulohypoxylon</i> sp. KYG-19 (family Xylariaceae), including three gymnomitrane-type sesquiterpenes xylariacinols A, B, and D (<b>1</b>, <b>2</b>, and <b>4</b>), one bisabolane-type sesquiterpene annulnol F (<b>6</b>), one phenol derivative lariacinol G (<b>7</b>), and two polyhydroxy compounds hypoxylonols H and I (<b>8</b> and <b>9</b>), together with two known gymnomitrane-type sesquiterpenes emericellin A (<b>3</b>) and 3-gymnomitren-15-ol (<b>5</b>). The assignments of their structures was determined by extensive spectroscopic and spectrometric analysis, acetonide analysis, Mosher's method, and X-ray crystallography. In addition, the structures of emericellins A and B, which were reported to possess an unprecedented tricyclo[4, 4, 2, 1]hendecane scaffold, were revised by comparing their spectroscopic data with those of <b>1</b> and <b>3</b>. Compounds <b>1</b> and <b>4</b> exhibited antibacterial activity against <i>Escherichia coli</i> with minimum inhibitory concentrations of 4 and 2 μg/mL, respectively.