子囊菌门（Ascomycota）是真菌界中种类最多的一个门，其中除酵母亚门为单细胞外，其余种类都是多细胞的，有分枝、有隔的菌丝组成的。

在无性繁殖时，会出芽或分生孢子；有性繁殖时都能形成有盖或无盖的、棒状或卵形的子囊，通常子囊内进行减数分裂生成八个子囊孢子，子囊分散、单细胞种类子囊裸露、多细胞种类子囊包在由菌丝结成的子实体内，称为子囊果。

子囊菌门的真菌都是寄生或腐生，对人类生活非常重要的有酵母菌、冬虫夏草、青霉菌、可以食用的羊肚菌等，也有很多种为植物致病菌。

Ascomycota is a division or phylum of the kingdom Fungi that, together with the Basidiomycota, form the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. They are the largest phylum of Fungi, with over 64,000 species. The defining feature of this fungal group is the "ascus" (from Greek: ἀσκός (askos), meaning "sac" or "wineskin"), a microscopic sexual structure in which nonmotile spores, called ascospores, are formed. However, some species of the Ascomycota are ****, meaning that they do not have a sexual cycle and thus do not form asci or ascospores. Previously placed in the Deuteromycota along with ****ual species from other fungal taxa, ****ual (or anamorphic) ascomycetes are now identified and classified based on morphological or physiological similarities to ascus-bearing taxa, and by phylogenetic analyses of DNA sequences.