《绿衣骑士》这部电影，其实改编自一首十四世纪英国的头韵诗《高文爵士和绿衣骑士》（Sir Gawain and the Green Knight），是一首亚瑟王传说体系中关于骑士的浪漫诗歌。
圣诞前夜，亚瑟王和他的骑士们聚集在大殿，此时一名身着绿衣，骑着绿马，举着绿色冬青树枝的骑士突然闯，他要求来一场友好的，他拿出了自己的斧头，说有勇气的人可以用这个斧头来他，并且这个斧头也送给这位勇者，只是一年后的今天，绿衣骑士将把今天受的伤如数奉还。
众骑士都吓破了胆，就在老亚瑟王准备亲自披挂上阵时，他的侄子，最年轻的爵士高文爵士（亚瑟王没有子嗣，所以高文是第一传承人）站了出来，绿骑士把脖子露出来，高文一斧子过去，绿骑士当场身首异处，只是绿衣骑士把自己的头颅捡起来，提醒高文一年后在绿色殿堂相见，便骑马离开。
一年后，高文爵士准备妥当开始寻找绿色殿堂，过五关斩六将，算是一路无双，直到他来到了一座城堡。城堡的主人是贝蒂拉克，城堡里还有贝蒂拉克美丽的妻子和一个丑陋的老妇人，贝蒂拉克说你看现在距离新年还有两天，绿色宫殿很近，干脆在我这里住几天，等时间到了再去赴约，高文爵士觉得蛮有道理，就答应了。
在等待的这三天中，贝蒂拉克向高文提出了一个：我把每天打猎到的猎物给你，你把每天获得的东西给我。第一天贝蒂拉克出去时，贝蒂拉克妻子来找高文，高文节操很高，于是妻子吻了高文一口，晚上贝蒂拉克打猎回来，高文给了贝蒂拉克一个亲亲，但也没说这吻怎么回事。
Sir Gawain and the Green Knight
Sir Gawain was Arthur’s nephew. In English stories, he is always described as a bre, honest and loyal knight.
According to the story, King Arthur and his Round Table Knights were holding their New Year’s banquet at Camelot when a tall knight dressed in green and riding on a green horse came in, holding a huge axe in his hand. He challenged a knight to cut his head off on condition that the knight agreed to he his head cut off a year after. Gawain accepted the challenge and cut off the Green Knight’s head.. The knight picked up his head and rode away.
Soon after that, Gawain set off to look for the Green Knight to receive his cut. After going through many strange adventures, on Christmas Eve Gawain came upon a beautiful castle where he was well entertained. He agreed to stay on till New Year’s Day since he was told that the Green Knight lived nearby. The lord of the castle made an agreement with Gawain that each day he himself would go hunting。
