Manuchar I Dadiani (Georgian: მანუჩარ I დადიანი; died 1611) was Prince of Mingrelia, of the House of Dadiani, from 1590 until his death. A younger son of Levan I Dadiani, he succeeded on the death of his elder brother, Mamia IV Dadiani.
Manuchar ruled over Mingrelia, in western Georgia, in a period of continuous anarchy in the successor states of the former kingdom of Georgia. Manuchar continued his predecessors' efforts to extend the Dadiani's influence over the kingdom of Imereti, Mingrelia's nominal suzerain. He fought off an invasion led by King Simon I of Kartli, who sought to reunite all of Georgia under his aegis, and secured his protégé Rostom on the throne of Imereti, thereby briefly restoring relative peace in western Georgia. Manuchar died in a hunting accident and was succeeded by his son, Levan II Dadiani.
Manuchar Dadiani was a younger son of Levan I Dadiani, Prince of Mingrelia. The date of his birth is unknown. He succeeded on the death of elder brother, Mamia IV Dadiani, in 1590. That same year, Simon I, king of Kingdom of Kartli in eastern Georgia, took advantage of instability in western Georgia and renewed his efforts to bring the Kingdom of Imereti under his control. He led his army, equipped with artillery, over the Likhi mountains into Imereti and forced its king Rostom, the Dadiani's nominee, into flight to Mingrelia. Dadiani offered to reinstate Rostom on terms of vassalage and himself promised peace and submission to Simon. The king of Kartli, however, insisted on Rostom being surrendered; else, he threatened to attack Mingrelia.
Manuchar responded with mobilization and, accompanied by Rostom and his loyalists, attacked Simon at Opshkviti, defeated him and captured his cannons. Simon fled to Kartli, while Rostom was restored in Imereti under Dadiani's protection. The two kings eventually reconciled and peace was reestablished, for the time being, in western Georgia. According to the 18th-century historian Prince Vakhushti, Manuchar died in a hunting incident, while pursuing a herd of deer, in 1611. He was succeeded by his son, Levan II Dadiani.