Most of the aliens on this list are a bit obscure, they are characters we’ve hardly met and species we haven’t explored, but you can’t say that about Q. The Q are an omnipotent race of beings that existed on an extra-dimensional plane known as the Q continuum, and their appearance usually meant fantastic Star Trek. Dealing with Q brought out the best and worst in humanity and the Federation, plus John de Lanice is a delight. Star Trek: Enterprise didn’t have a Q episode, and we missed him, bring back Q!
Next: The Yridian