Maeng (맹/孟) is an uncommon Korean Surname which means 'eminent and first in series' in Sino-Korean Language, similar to Chinese Meng. The origin of the family name Meng can be traced back to Qingfu of one distinguished family of the State of Lu and Meng Zhi of one distinguished family of the State of Wei, both in the Spring and Autumn Period (772-481 BCE). They were both descendents of the surname Ji.
After the founding of the Western Zhou (c. 1100-771 BCE), the Duke of Zhou, son of King Wen of Zhou and younger brother of King Wu of Zhou, was granted Lu as his feudatory and established the State of Lu. Later after internal unrests broke out in the State of Lu, Qingfu, son of the Dukr Xiang of Lu took power but was exiled and escaped to the State of Ju. The offspring of Qingfu returned to the State of Lu after the situation there stabilized and were given the title of "minister" and the hereditary post of minister of works of the State of Lu and the surname Meng or Mengsun was conferred on them.
The other branch of the surname Meng were from the State of Wei in the Spring and Autumn Period (772-481 BCE). The State of Wei was established by Kang Shu, a younger brother of the King Wu of Zhou, who was also of Ji family. According to historical records, Duke Ling of Wei had an elder brother Meng Zhi and the children of Meng Zhi thus took Meng as their family name. It is also recorded on the pedigree of Meng families that Duke Ling of Wei had a son called Gong Meng, whose offspring later picked Gongmeng as their surname, and then Meng for short.
Since North Song Dynasty (960-1127), as the status of Mencius (372-289 BCE) was improved, the families of Meng started to expanded in population and mainly lived in then "Pingchang" and "Wuwei". Mencius, also known as Maeng Ga in Korean (Hangul/Hanja: 맹가/孟軻) is the progenitor of Sinchang Maeng Clan (신창 맹씨/新昌孟氏), a clan which is originated from the Commune of Sinchang-myeon, Asan City, Southern Chungcheong Province.
Based on the 2000 Korean Republic Census - provided by Statistics Korea (통계청/統計廳/Tonggyecheong/KOSTAT), there are 20,219 people in 6,230 families who bear the surname of Maeng, mostly originated from Sinchang Maeng Clan. Hence, this clan is placed at 89th place in Korean Surnames List.
Maeng Seung-hoon (맹승훈/孟承訓), the 39th Generation-Descendant of Mencius traveled to Silla Dynasty in 888 - 2nd Reigning Year of Queen Jinseong Kim Won from his hometown, Chinese Tang Dynasty and became a scholar in the turbulent Later Three Kingdoms Period. Maeng Ui (맹의/孟儀), Count of Sinchang (신창백/新昌伯) who was the 51st Generation-Descendant of Mencius designated Sinchang Prefecture (신창현/新昌縣) as the ancestral seat of Maeng Clan during the reign of King Chungseon Wang Jang (1275-1325), 26th monarch of Goryeo Dynasty.
The most notable clansman is Maeng Sa-seong (맹사성/孟思誠; 1360-1438), a government official who served Goryeo Dynasty during its final days and Joseon Dynasty since the foundation of that dynasty by King Taejo Yi Seong-gye. He became the Prime Minister of Joseon Dynasty, outlived First Three Kings of Joseon Dynasty: Taejo Yi Seong-gye, Jeongjong Yi Bang-gwa and Taejong Yi Bang-won. He died in the 20th Reigning Year of King Sejong the Great (1438).