Is many a singular or plural noun?

Answer 1

Many can be used as a determiner, pronoun, adjective, and noun, and verbs are conjugated in the plural, e.g. the fans cheered their team on but many weredisapointed with their performance.

Answer 2

Neither. Many is actually an adjective, to describe a noun. It has come to be used as a noun on the sense of "a good many of them were late", in which case it is a plural noun.