Eleven new 9,10-seco-cycloartan triterpene glycosides (1-11), seven new lanostane triterpene glycosides (12-18), and two new ursane triterpenoids (19-20) were isolated from the twigs and leaves of Lyonia ovalifolia. The structures of these compounds were elucidated by extensive MS and NMR spectroscopic analysis. The absolute configuration of compound 1a (the aglycone of 1) was established by X-ray crystallography, and that of C-24 in compounds 2, 7, and 12 was established by Mo2(OAc)4-induced electronic circular dichroism experiments. All compounds were evaluated for their antiviral [herpes simplex virus-1 (HSV-1), influenza A/95-359 (A/95-359), and Coxsackie B3 (CVB3)] activity. Compounds 1, 1a, 2a, 12a, 13, and 16 exhibited potent activity against HSV-1, with IC50 values from 2.1 to 14.3 μM, while compounds 1a, 2a, 12a, 13, and 12-2a exhibited potent activity against A/95-359, with IC50 values from 2.1 to 11.1 μM. In turn, compounds 1, 1a, 2a, 12a, and 13 exhibited potent activity against CVB3, with IC50 values from 2.1 to 11.1 μM.