Final answer:
The protagonist of 'Sir Gawain and the Green Knight' is Sir Gawain, and the antagonist is the Green Knight, who is also known as Bertilak. The story revolves around the challenges that Gawain faces and the moral lessons he learns from his interactions with the Green Knight.
Step-by-step explanation:
In the poem Sir Gawain and the Green Knight, the protagonist is Sir Gawain himself, as he is the main character around whom the story revolves and with whom we follow the moral and chivalric challenges. On the other hand, the antagonist is the Green Knight, also known as Bertilak, who presents these challenges and stands in opposition to Sir Gawain, creating the central conflict of the story. It's worth noting that the Green Knight/Bertilak may not be an antagonist in the traditional sense of being a villain, as he facilitates Gawain's character development. The narrative includes themes of heroism, integrity, and human fallibility, with the figure of the Green Knight symbolizing the trials that test Sir Gawain's virtues.