The story of Jonathan Livingston Seagull centers primarily around the title character. There really are not any other main characters. There are a few other characters that are significant in telling his story and who are worth mentioning.
One such character is Elder Gull. He is the leader of the flock's council. He represents an older conservative viewpoint that has no predilection or appreciation for experimentation and pushing limits. It is he who banishes Jonathan from the Flock.
Old Chiang, otherwise known as The Great Gull, is an old and sagacious bird who instructs Jonathan on the true meaning of life and how to transport himself anywhere in the universe with a mere thought. Love, old Chiang tells Jonathan, is the highest of all achievements. This is not just the love of others, but also the love of oneself. In many ways, Old Chiang is a stand-in for the divine. He is a repository for all the knowledge and wisdom of the universe.
Fletcher Lynd Seagull is one of Jonathan's main pupils after he returns to his old flock. Fletcher believes that flying is a gift that is to enjoyed and taken to its greatest limits. As a result, he is cast out of the flock. Fletcher is keen to learn the lessons that Jonathan has to teach him. Fletcher is young and eager. He also has a developed sense of justice. Fletcher is an apt learner who takes Jonathan's lessons to heart. However, he remains judgemental of the flock that made him an outcast. His greatest struggle is learning to forgive his old companions.
Martin William Seagull is a lesser but still important character. He is one of Jonathan's other pupils. Though crippled, he learns to fly expertly at low speeds under Jonathan's tutelage.