) is a structure or organ of the gametophyte phase of certain plants producing and containing the sperm or male gametes. It is present in lower plants like mosses and ferns, but the comparable structure in gymnosperms (microsporangium) and angiosperms (anthers) is comprised mostly of sporophyte (diploid) tissue that surrounds the haploid gametes. The female counterpart to the antheridium is the archegonium
In mosses, the anteridium is borne on an antheridiophore
. Some ascomycetes, water moulds and algae also have antheridia during their reproductive stages.