A fabulist is a storyteller. Your uncle who spends holiday gatherings telling stories that end with clear morals is a fabulist, and so is your cousin who invents long, complicated excuses for being late to school every morning.
Someone who writes or recites fables — moralistic tales that often feature animals as characters — is one kind of fabulist. The ancient Greek fabulist Aesop, for example, composed many stories about talking animals that ended with important moral lessons. Another kind of fabulist is a person who tells tall tales, or who lies. The root of fabulist is the Old French fable, "lie or pretense," from the Latin fabula, "story, play, or tale," or literally, "that which is told."