Necrotrophic plant pathogenic Ascomycota require dead host plant tissue to obtain nutrients for growth and reproduction. In interactions between plants and necrotrophic fungi, successful infection relies on the programmed cell death-inducing activity of compounds secreted by the fungus, which are referred to as necrotrophic effectors. These compounds can either be proteins, small modified peptides, or secondary metabolites. Their cell death-inducing capability allows the fungus to hijack the plant immune system for its own benefit and contribute to fungal virulence in a quantitative manner. In this chapter we first describe the effector repertoire in several genera of necrotrophic Ascomycota. Next, we discuss case studies that enabled to identify the cellular targets of specific effectors in different plant species. Finally, we present an overview of tools and methodologies to identify novel necrotrophic effectors and to assess their importance for fungal virulence. This knowledge will contribute to the selection of plant genotypes displaying increased resistance to diseases caused by necrotrophic Ascomycota.