In most cases, yes. The majority of schools around the world prefer that you have a 4-year college degree; many will not hire a teacher without one. In most locations in Asia—as well as in some other countries—it is a requirement in order to receive a work visa. However, in a few places, teachers without degrees can sometimes qualify to teach English. If you do not have a college degree, it is best to ask about the specific location in which you are interested.