Sanchao beimeng huibian 三朝北盟會編 "Collection of documents concerning alliances with the north during the three reigns" is a 250-juan long history of the relationship between the Song 宋 (960-1279) and the Jin 金 (1115-1234) empires during the three reigns of the emperors Huizong 宋徽宗 (r. 1100-1125), Qinzong 宋欽宗 (r. 1125-1126), and Emperor Gaozong 宋高宗 (r. 1127-1162). It was written by Xu Mengxin 徐夢莘 (1124-1207), courtesy name Shanglao 商老, who, although passing the metropolitan examination, never occupied an official post.
Xu's history is a valuable report of the wars and treaties (meng 盟) between the Song dynasty that had to flee the old capital of Kaifeng 開封 (modern Kaifeng, Henan), and the Jin dynasty that conquered the whole northern part of China. Xu collected the report of several hundred eye-witnesses of the downfall of the Northern and the establishing of the Southern Song, as well as official documents, compared the texts and eliminated discrepancies and contradictions. Xu submitted his book to the throne in 1196, and at the court it was valued to such a high degree that it served as the main material for the compilation of the Gaozong shilu 高宗實錄, the veritable records of Emperor Gaozong.
A supplement in 50 juan, also written by Xu Mengxin and called Beimeng jibu 北盟集補, is lost.
The book beginns with the treaty of Haishang 海上之盟 concluded in 1117 between the Song and the Jin empires. Its central part deals with the "catastrophy" of the short Jingkang reign 靖康 (1126), in Chinese called Jiankang zhi huo 靖康之禍, and the book ends with the assassination of the Jin emperor Prince Hailing 海陵王 in 1161.
The Sanchao beimeng huibian is particularly valuable because it contains unrevised original material, which is rarely seen in other sources. Shorter histories on that period, like the Jianyan tongwen lu 建炎通問錄 (1127-1130), Shunchang pozei lu 順昌破賊錄, Jingkang xiaoya 靖康小雅, or Weiqilu 偽齊錄, are excerpts of the Sanchao.