The phytochemical study of the aerial parts of Artemisia sylvatica (Asteraceae) led to the isolation of nine sesquiterpene lactones, l$alpha$-hydroperoxy-rupicolin A acetate (1), rupicolin B acetate (2), rupicolin A acetate (3), l$alpha$-hydroxy-4$alpha$-hydroperoxy-bishopsolicepolide (4), 1$alpha$-hydroperoxy-4$eta$-hydroxy-8$alpha$-acetoxy-guaia-2,9,11 (13)-triene-6$alpha$,12-oxide (5), 1$alpha$-hydroperoxy-4$alpha$-hydroxybishopsolicepolide (6), l$alpha$,4$eta$-dihydroxy-8$alpha$-acetoxy-guaia-2,9,11(13)-triene-6$alpha$,12-olive (7), rupicolin A (8) and l$alpha$,4$alpha$-dihydroxy-bishopsolicepolide (9). Their structures were established by chemical and spectroscopic methods.