The Yà Ângà Âijà Âng () or Chief State Councilor was a member of the State Council of Joseon and the highest government position in the Joseon period of Korean history. The Yà Ângà Âijà Âng held roles similar to a modern-day prime minister of a presidential system. As the senior member of the Chief State Council, the Yà Ângà Âijà Âng participated in the administration of general government affairs alongside the Chwaà Âijà Âng and Uà Âijà Âng.
The title was created in 1400 with the creation of the State Council. Existing for over 500 years, the function was handed over in 1895 during the Kabo Reform to the newly-formed position of the Prime Minister of the Korean Empire. Only one official, usually an elder who had previously served as Chwaà Âijà Âng, was allowed to assume the position of Yà Ângà Âijà Âng. The Yà Ângà Âijà Âng was also referred to as Yà Ângsang (), Sangsang (), Sugyu () or Wà Ânbo ().
Although the title of Yà Ângà Âijà Âng was legally defined as the highest post in charge of all state affairs, its practical roles and powers shifted drastically throughout history as the roles of the State Council were not clearly defined in the Kyà Ângguk taejà Ân. During the early years of Joseon, the Yà Ângà Âijà Âng saw limited roles in government as the Six Ministries reported directly to the king.
Upon its founding in 1392, the state of Joseon initially inherited the state structure of its predecessor Goryeo (918âÂÂ1392). In 1400, the second year of his reign, King Jeongjong reformed the ("Privy Council"), which was previously the supreme administrative body of the Goryeo dynasty, to the State Council. The head of the State Council was given the title "Yà Ângà Âijà Âng pusa" (). As both functions of State Council got stronger, and its system was further revised, "Yà Ângà Âijà Âng pusa" was renamed to "Yà Ângà Âijà Âng" in a firm establishment of the office.
In 1466, the position was officially put in statutory form with the finalization of the Kyà Ângguk taejà Ân. The Yà Ângà Âijà Âng title was generally conferred on a senior minister who had previously served as Chwaà Âijà Âng (Left State Councilor), a post immediately below that of Yà Ângà Âijà Âng, but higher than that of Uà Âijà Âng (Right State Councillor). The three councilors were collectively known as the "Chà Ângsà Âng" (), or "Samà Âijà Âng" ().
Until April 1436, the 18th year of Sejong the Great's reign, Chwaà Âijà Âng and Uà Âijà Âng concurrently served as Panijosa (å¤åÂÂæ¹äºÂ) and Panbyeongjosa (å¤堵æ¹äºÂ) respectively, so that they governed personnel affairs of yangban (the literary and military nobility).
Yà Ângà Âijà Âng continued to exist as an honorary post, and so only managed to contemplate and adjust diplomatic documents or re-examine the cases of condemned people.
However, when Hwang Hà Âi was appointed as "Yà Ângà Âijà Âng pusa" in that same year, Sejong modified the government system to strengthen the power of Chà Ângsà Âng from the Six Ministries centered system. With the reform, Sejong noted that a situation in which three highest senior advisors could not participate in the state affairs contravened the original intention to have them as the high state councillors.
During the reform, Six Ministries conferred with State Council regarding the responsibilities of each minister. State Council discussed legitimacy of the issues, and then reported to the king. After receiving an approval from the king, State Council returned to Yujo to enact the assigned affairs. As a result, Yà Ângà Âijà Âng came to participate more actively in the representative work as the head of State Council. However, other ministerial duities, such as those of the ministries (Ministry of Personnel) and (Ministry of Military Affairs) to implement personnel management, Pyongjo's mobilization of soldiers, (Ministry of Punishments)'s right to handle all criminals other than condemned people, were still directly operated by the related ministers.
When Prince Suyang usurped the place of his nephew, King Danjong, the function of Yà Ângà Âijà Âng was relegated to its previous powerless position. This was because when the King Sejo was still a prince, his actions were greatly restricted by his political rivals, Yà Ângà Âijà Âng, Hwangbo In and Chwaà Âijà Âng, Kim Chongsà Â. So during the reigns of King Seongjong and Jungjong, there were several proposals to restore the former powers of State Council, but those suggestions were not implemented.
Major affairs of the state were discussed when Bibyeonsa was established in 1558 (during the 10th year of King Myeongjong's reign). The three High Councillors attended meetings only as "Tojejo" (Supreme Commissioner). So the power of Yà Ângà Âijà Âng tended to be increased or decreased, depending on the political atmosphere of the times, such as the degree of the king's power, the relationship between State Council and Six Ministries, the establishment of the Border Defense Council, the later administration of Kyujanggak (the Royal Library), the conflicts between political parties, and the advancement of "in-law government" (), among others. Regardless, the title "Yà Ângà Âijà Âng" continued as the apex in the bureaucratic system throughout the entire Joseon period.