Cho Kwangjo (Korean: 조광조; Hanja: 趙光祖, 23 August 1482 – 10 January 1520), also called by his art name Chŏngam (정암), was a Korean Neo-Confucian scholar who pursued radical reforms during the reign of Jungjong of Joseon in the early 16th century.

He was framed with charges of factionalism by the power elite that opposed his reform measures and was sentenced to drink poison in the Third Literati Purge of 1519. He has been widely venerated as a Confucian martyr and an embodiment of "seonbi spirit" by later generations in Korea. Some historians consider him one of the most influential figures in 16th century Korea. He is known as one of the 18 Sages of Korea (동방18현) and is enshrined in the Munmyo.

Cho Kwangjo was the son of Cho Wŏngang (조원강; 趙元綱) and was from the Hanyang Cho clan [ko]. Cho studied under the Neo-Confucian scholar Kim Koengp'il [ko], Kim Chong-jik's disciple who was in exile at the time following the First Literati Purge of 1498. When Kim Koengp'il was later executed (by poison) following the Second Literati Purge of 1504, Cho was exiled for being Kim's disciple.

At this time, Joseon Dynasty politics were primarily marked by the power struggle between two aristocratic yangban factions - the established "Hungu" power elites who were generally conservative and the upstart Sarim scholars called seonbis, who belonged to the Neo-Confucian school of Kim Chong-jik and other thinkers. The Sarim faction had entered court politics during the reign of King Seongjong in the late 15th century but suffered two bloody purges under his successor Yeonsangun. When Yeonsangun was eventually deposed in 1506, Jungjong was placed on the throne as the eleventh king of Joseon by the Hungu leaders who led the coup. For first ten years of his reign, Jungjong could not truly rule the country with regal authority (he was forced to depose his faithful queen because her father was killed by the coup leaders, and they feared that the queen might take revenge.) However, three main coup leaders died of natural causes by then, and Jungjong began to welcome Sarim scholars to his court to check the Hungu faction's power. The Sarim faction considered the Hungu faction as a whole as greedy and corrupt men unworthy of respect and sought to establish an ideal neo-Confucian society. Indeed, many of coup leaders had enjoyed Yeonsangun's favor during most of his reign, and their leader Pak Wŏnjong led the coup mainly for personal revenge for his older sister who had rumors of adultery.

Cho Kwangjo came from a prominent family that belonged to the Hungu faction but was called "crazy man" and "source of disaster" by people around him for studying neo-Confucianism under exiled Sarim scholar Kim Koengp'il at the height of persecution of the Sarim faction. In 1510, Cho passed the kwagŏ exam and became a student at the Sungkyunkwan. He was often recommended for a court position by high officials and fellow students at the Sungkyunkwan, but he delayed entering civil service to pursue further study until 1515, when he was recommended to King Jungjong by Minister of Personnel An Tang along with 200 Sungkyunkwan students and was immediately appointed to a position of junior sixth rank. However, he was ashamed to take office with others' help and took Al-seung-si exam, and his essay caught Jungjong's attention.

By then, Cho was already known for his unbending and outspoken character as he soon emerged as the leader of the Sarim faction. For instance, when he became a jung-un, lowest position at Office of Censors, the first thing he did on the following day was to petition the king to fire all his superiors at the Office of Censors and Office of Inspector General. At the time, two Sarim officials had petitioned the king to restore status of the deposed queen, who was deposed by the Hungu faction. The Office of Inspector General and Office of Censors had them exiled for their impertinent petition. Cho argued that two offices violated their given function by suppressing free speech and petitioned the king to fire his superiors or accept his resignation since he could not work with them. To the surprise of everyone, Jungjong replaced everyone in two offices except Cho. This event reflected Jungjong's complete trust and confidence in Cho, who rose in a series of unprecedented promotions from rank of junior sixth rank to junior second rank in only three years.

King Jungjong wanted to bring new talents to the royal court that was dominated by the Hungu faction, and Cho complied by introducing a new system of government recruitment via recommendations that were based on the candidates' moral character as well as scholarship. He argued that existing officer examination were too philosophical and placed too much emphasis on literary skills, detached from the practical needs of the government. The supplementary recommendation examination that Cho introduced was called an "examination of the Sage and Good" (현량과; 賢良科; hyŏllyang-kwa). This was an abbreviated examination for candidates recommended by local magistrates as men of highest integrity in the presence of the king, who chose the winning candidates. This system allowed Cho to recruit many talented Sarim scholars who had been living a secluded life in rural provinces. However, it also left him open to Hungu faction's attack.

Cho and his supporters then pushed forth a series of radical reforms as they established local self-government system called Hyang'yak to strengthen local autonomy and communal spirit among people. In this system, deference was placed according to seniority of villagers rather than their social status. The Sarim faction also sought to reduce gap between the rich and poor with a land reform that would distribute land to farmers equally and limit amount of land and number of slaves that one could own. This measure also targeted Hungu faction's accumulation of land and wealth.