Manuchar II Dadiani (Georgian: მანუჩარ II დადიანი; died c. 1840), of the House of Dadiani, was Prince of Mingrelia from 1791 to 1793 as a rival to his elder brother, Grigol Dadiani, whose rule was marred by the long-standing struggle between the Imeretian crown seeking to subdue Mingrelia and Mingrelian efforts to win full independence, a continuation of the conflict which had plagued western Georgia for centuries. After the brothers reconciled in 1799, Manuchar was appanaged with Salipartiano, which he lost to his nephew Levan, a new Prince of Mingrelia, in the wake of Grigol's death in 1804.
Manuchar was a son of Katsia II Dadiani by his third wife Anna Tsulukidze. In 1791, King Solomon II of Imereti, who sought to unite all of western Georgia under his authority, deposed Grigol and replaced him by a more amenable Manuchar. In 1792, Grigol's attempt at comeback were dashed as his newfound ally David II, claimant to the Imeretian crown, was defeated by Solomon and Manuchar near Kutaisi and Grigol's Abkhaz reinforcements deserted. Grigol later found support in the district of Lechkhumi and successfully resisted Solomon and Manuchar in his stronghold at Nogi. Manuchar was eventually ousted from Mingrelia and fled to Abkhazia in 1794, but Grigol was able to buy the Abkhaz ruler Kelesh Bey's loyalty by granting him the fort of Anaklia. There was another claimant in Mingrelia during these years: Tariel, younger brother of Grigol and Manuchar.
The Dadiani brothers reconciled in 1799. Grigol was recognized as Prince of Mingrelia, while Manuchar received the fief of Salipartiano. In a renewed conflict between Imereti and Mingrelia in 1802, Solomon again attempted to enlist Manuchar, but the latter eventually stood by his brother's side. Grigol died in October 1804, a few months after he placed his principality under Russian suzerainty. His young son and successor Levan was placed under regency of the princess dowager Nino. Manuchar saw this as an opportunity to advance his claims to the Mingrelian throne and petitioned the Russian authorities to confirm him as the next ruler of Mingrelia or, at least, to leave Salipartiano in his possession. The Russians turned down Manuchar's request as well as his mother's intercession; in 1805, Salipartiano became a Mingrelian crown land and Manuchar was relegated to his reduced estates.