We analyzed the phylogenetic relationships between eight Aphidius Nees and six Lysaphidus Smith species on the basis of 12 morphological characters by parsimony analysis. The consensus tree does not support the generic status of Lysaphidus. Aphidius iranicus, sp. nov., associated with Titanosiphon bellicosum Nevsky on Artemisia absinthium L. from Iran, is described. The new parasitoid species is described and illustrated by line drawings, and its diagnostic characters are discussed. The taxonomic position of the subgenus Tremblayia Tizado and Núñez-Pérez is also considered. Tremblayia and Lysaphidus are newly classified as synonyms of Aphidius. The following new or revised combinations are proposed: Aphidius adelocarinus Smith, comb. rev., A. ramythirus Smith, comb. rev., A. rosaphidis Smith, comb. rev., A. viaticus (Sedlag), comb. nov., A. arvensis (Starý), comb. nov., and A. erysimi (Starý), comb. nov.