Ophiostomatoid fungi are commercially and economically important group of fungi in forestry and timber production. This group is represented by several genera of Ascomycetes with common morphological characteristics, although withdistinct taxonomy and phylogeny. Several genera of ophiostomatoid fungi have been considered synonymous solely based on morphological similarities as a result of an adaptation to insect dispersal. Ophiostomatoid fungi cause considerable economic losses in the forestry and timber production due to sap stain and vascular wilt diseases. The threat of introduced ophiostomatoid fungi is increasing with the global timber trade and loose control measurements. An overview of the taxonomy, ecology, concept of association (mutualism/symbiosis) and the economic importance of ophiostomatoid fungi are provided