Microsynodontis nannoculus is a species of upside-down catfish endemic to Equatorial Guinea where it occurs in the Kyé River.

[2] However, when examining previously collected specimens from the lower Guinea region that had been identified as M. batesii, Dr. Ng discovered that the specimens actually consisted of nine distinct species, eight of them previously undescribed.

[3] M. nannoculus is a small fish, reaching a maximum standard length of 3.9 centimeters (1.5 in).

[1] The mouth of the fish faces downward, with broad lips containing papilla.

[4] M. nannoculus can be distinguished from other members of the genus Microsynodontis by examining the size of the eye.