Ergot (pron. /ˈɜːrɡət/ UR-gət) or ergot fungi refers to a group of fungi of the genus Claviceps.

The most prominent member of this group is Claviceps purpurea ("rye ergot fungus"). This fungus grows on rye and related plants, and produces alkaloids that can cause ergotism in humans and other mammals who consume grains contaminated with its fruiting structure (called ergot sclerotium).