东汉末年乱世中，刘备的两位夫人、以及一位未过门的小妾绮兰（孙俪 饰）受困曹营，关云长（甄子丹 饰）为存忠义投降曹操（姜文 饰），但始终不能原谅曹操操控汉室的狼子野心，希望能够重回刘备身边。曹操倾慕关羽之将才以及仁者之心，试图用天下苍生之利益说服后者。适逢袁绍起兵伐曹，关云长于阵斩杀颜良，获封汉寿亭侯，并与张辽（邵兵 饰）结下同袍之谊。曹操将两位刘夫人遣返后，在关云长酒中加入春药，欲使其与绮兰发生不义关系——关云长昔日对同乡绮兰暗怀情意，甚至曾经不惜为她杀死官兵，这段感情终究被叔嫂之礼阻断，清醒过来的关云长携绮兰投奔刘备，沿路冲破重重关卡，留下“过五关斩六将”的千古传奇……This historical martial arts film adapted from the story of Guan Yu crossing five passes and slaying six generals in Luo Guanzhong's historical novel Romance of the Three Kingdoms. In AD 200 during the late Eastern Han Dynasty, Cao Cao eliminates his political opponents Dong Cheng and others, before turning his attention towards rival warlords Liu Bei and Yuan Shao. To avoid fighting a war on two fronts, Cao Cao decides to attack Liu Bei first. Liu Bei flees north to join Yuan Shao, while his family is captured by the enemy. Liu Bei's sworn brother Guan Yu (Donnie Yen), surrenders to Cao Cao to uphold his oath of brotherhood and preserve his honor. Cao Cao knows he's a great warrior & hopes that Guan Yu will continue serving him. Meanwhile, Guan Yu is secretly in love with his sworn brother's concubine Qilan, but is afraid to express his feelings to her. Qilan reproaches Guan Yu for serving Cao Cao. By then, Guan Yu has also received news of Liu Bei's whereabouts, so he prepares to leave Cao Cao to deliver Liu Bei's fiancé, Qilan, to him. Cao Cao is unable to stop Guan Yu and gives orders for the defending generals at the various passes to let Guan Yu through. Despite so, Cao Cao's followers feel that Guan Yu will become a threat to them if he succeeds in escaping, so they plot to have Guan killed. Guan Yu then embarks on a dangerous long journey through the passes to reunite with Liu Bei.