The Fescue aphid or Grass aphid, Metopolophium festucae, is a pest of forage grasses, wheat, and other small grains in its native range in the United Kingdom and parts of Europe. It is an adventive pest in the Pacific Northwest, USA, several countries in South America, and in New Zealand. Infestations in small grains globally are attributed almost exclusively to the subspecies, M. festucae cerealium. Large populations of the subspecies coupled with evident phytotoxicity caused by its feeding contribute to its pest status. Although the literature on the species is relatively sparse, a chapter is included in this volume because of its newly invasive infestations, especially in North America since 2011. Covered are its distribution, host range, possible role as a virus vector, potential for host plant resistance in wheat, and general guidelines for its management. A research agenda to address knowledge gaps concerning the species and its management are outlined.