Gametangium

: gametangia) is a sex organ or cell in which gametes are produced that is found in many multicellular protists, algae, fungi, and the gametophytes of plants.

In contrast to gametogenesis in animals, a gametangium is a haploid structure and formation of gametes does not involve meiosis.

In flowering plants, they are replaced by the embryo sac inside the ovule.

Antheridia are common in the gametophytes in "lower" plants such as bryophytes, ferns, cycads and ginkgo.

For example, in zygomycetes, two gametangia (single multinucleate cells at the end of hyphae) form good contact with each other and fuse into a zygosporangium.