Aegilops is the most closely related genus to Triticum in the tribe Triticeae. Aegilops speltoides Tausch (B genome donor) and Ae. tauschii Coss. (D genome donor) contributed two of the three genomes present in common wheat (Triticum aestivum L., 2n = 6× = 42, AABBDD genomes). The Aegilops genus consists of 10 diploid and 12 polyploid species, all can be crossed readily with common wheat and represent a large reservoir of agronomically useful genes that can be exploited in wheat improvement. Since the 1950s, many unique genes for disease and pest resistance have been transferred into wheat from various Aegilops species. In this chapter we review all formally named genes transferred from Aegilops species into wheat except those transferred from Ae. tauschii, which belongs to the primary gene pool of wheat and is covered in a separate chapter. This review provides useful information to wheat breeders on the available resistant germplasm for breeding programs. It also provides guidance to cytogeneticists to further utilize chromosome engineering to directly develop agronomically superior germplasm with good disease and pest resistance.