Cui Yan (165–216), courtesy name Jigui, was a Chinese politician serving under the warlord Cao Cao during the late Eastern Han dynasty of China. In his early life, he served briefly in the local district office before leaving home to study under the tutelage of the Confucian scholar Zheng Xuan. In the late 190s, Cui Yan became a subordinate of the northern warlord Yuan Shao but did not make any significant achievements under the latter, who ignored his suggestions. Following Yuan Shao's death in 202, Cui Yan was imprisoned when he refused to help either of Yuan's sons—Yuan Shang and Yuan Tan—in their struggle over their father's territories. After he was freed, Cui Yan came to serve under Cao Cao, the de facto head of the Han central government. Throughout his years of service under Cao Cao, Cui Yan performed his duties faithfully and diligently, maintaining law and order within his bureau and recommending talents to join the civil service. In 216, in an incident widely regarded as a case of grievous injustice, Cui Yan was accused of defaming Cao Cao in a letter and ended up being stripped of his post, thrown into prison and subsequently forced to commit suicide.

Cui Yan was from Dongwucheng County (東武城縣), Qinghe Commandery, Ji Province, which is around present-day Gucheng County, Hebei. He was born in the Cui family of Qinghe Commandery, a political family which rose to prominence during the Sui and Tang dynasties later. In his youth, he was known to be plain, dull and lacking in communication skills, but he was very interested in swordsmanship and military arts. When he was 22 years old, he was nominated by the local district office to be a judicial officer, for which he was so grateful that he started reading books such as the Analects and Han Shi (韓詩)

Six years later, at the age of 28, Cui Yan befriended Gongsun Fang (公孫方) and others and they studied together under the tutelage of the Confucian scholar Zheng Xuan. However, in 194, before Cui Yan could even complete his first year of studies, the Yellow Turban rebels from Xu Province attacked Beihai Commandery, where Zheng Xuan conducted his classes, so Zheng and his students fled east to Mount Buqi (不其山; northwest of Mount Lao) to evade chaos. Despite so, the rebellion had resulted in food shortages, so Zheng Xuan had no choice but to send his students away. After leaving Mount Buqi, Cui Yan could not return to Qinghe Commandery because rebel forces and bandits were rampant in the region and the roads leading west were blocked. He wandered around Qing, Xu, Yan and Yu provinces and visited several places, including Shouchun (壽春; present-day Shou County, Anhui), Lake Tai and the northern bank of the Yangtze River. After four years, he returned home and spent his time playing music and writing calligraphy.

Around the late 190s, the northern warlord Yuan Shao heard of Cui Yan and recruited the latter to serve under him. At the time, due to widespread chaos and famine, many soldiers had resorted to crime as a means of survival and some started robbing and plundering tombs. Cui Yan urged Yuan Shao to maintain good discipline among his troops, saying, "In the past, Sun Qing once said: 'If the soldiers in an army are ill disciplined, the army's prowess will be weak. It will not achieve victory even if it was led by either Tang of Shang or King Wu of Zhou.' As of now, the roads are covered with the remains of the dead and the people have yet to see your virtuous deeds. You should order all commandery and county officials to ensure that the dead are properly buried, so as to showcase your sympathy and compassion by following the benevolent acts of King Wen of Zhou." Yuan Shao appointed Cui Yan as a Cavalry Commandant (騎都尉).

In 200 CE, when Yuan Shao was preparing for a campaign against a rival warlord Cao Cao, he set up military garrisons at Liyang (黎陽) and Yan Ford (延津). Cui Yan attempted to dissuade him from going to war by saying, "The Emperor is in Xu and the people's hopes are with him. Why don't you faithfully perform your duties by defending the border and maintaining peace within your jurisdiction?" Yuan Shao refused to listen to Cui Yan and insisted on attacking Cao Cao, but ended up being defeated by Cao at the decisive Battle of Guandu later that year. After Yuan Shao died in 202, his sons Yuan Tan and Yuan Shang formed their own military forces and started fighting for control over their father's territories in northern China. Both Yuan Tan and Yuan Shang wanted Cui Yan on their side, but Cui refused to help either of them and claimed that he was ill. As a consequence, he was imprisoned by Yuan Shang, but was later saved by Yin Kui (陰夔) and Chen Lin.

In 205, after Cao Cao had defeated the Yuan brothers and taken over Ji Province, he wanted to recruit Cui Yan to serve as an aide-de-camp (別駕從事) under him. He told the latter, "According to official records, there are 300,000 troops under my command now. (Ji Province) is indeed a large province." Cui Yan replied, "The Empire is in a state of chaos and the Nine Provinces are divided, while the Yuan brothers fight among themselves and the bodies of the dead are scattered throughout the wilderness. The people have yet to see how your forces will bring benevolent rule and relief aid to them and liberate them from war and disaster, but now the first thing you do is to check the records for the numbers of troops and military equipment you've obtained. Is this what the people in this province expect of you?" Those present at the scene were all startled by Cui Yan's response. Cao Cao's facial expression changed and he thanked Cui Yan for his advice.

In the following year, when Cao Cao left Ji Province to attack Yuan Shao's nephew Gao Gan in Bing Province, he left his son Cao Pi in charge of Ye, the capital of Ji Province, and instructed Cui Yan to mentor Cao Pi. Once, when Cao Pi went on a hunting excursion to enjoy himself, Cui Yan wrote a long letter to him, haranguing the former on overly indulging in personal pleasures and neglecting his duties. Cao Pi later sent a reply, stating that he had destroyed his hunting equipment and thanking Cui Yan for his lecture.

In 208, when Cao Cao became the Han Chancellor, Cui Yan was appointed as a Senior Clerk in the East and West Bureaus (東西曹掾屬). The order from the Han imperial court conferring the appointment on Cui Yan read, "You possess the style of Boyi and the integrity of Shi Yu (史魚). Corrupt officials will mend their ways out of admiration for you while men of valour will strive harder after being inspired by you. You will be serving as a role model in these times, therefore you are hereby appointed to the East Bureau."