Jinjuichthys is an extinct genus of ray-finned fish, possibly an ichthyodectiform, from the Early Cretaceous (Albian) of South Korea.

The generic name Jinjuichthys means 'fish of Jinju' based on the city with the same name to which its type locality Jinju Formation belongs, while the specific name cheongi references the Korean geologist Cheong Chang Hi in honor of his contributions to the understanding of the biogeography of Korea. The holotype (PSU V 1011) is a relatively complete skeleton that lacks the caudal region, with an estimated standard length of 18.7 centimetres (7.4 in), while the paratype (PSU V 1012) consists of the caudal skeleton and caudal fin (the posterior part).^[1]

Jinjuichthys is included within the family Chuhsiungichthyidae along with Chuhsiungichthys and Mesoclupea, which has been traditionally placed within the order Ichthyodectiformes.^[1] However, the paleontologist Jesús Alvarado-Ortega questioned the placement of Bardackichthys and members of Chuhsiungichthyidae (especially Jinjuichthys and Mesoclupea) among this taxonomic order in 2024. He argued that diagnostic ichthyodectiforms should preserve the uroneurals in lateral position and have two separated longitudinal cavities, but the known specimens of Jinjuichthys show that its uroneurals are in dorsal position and that it had three or four longitudinal cavities. Jinjuichthys also lacked other diagnostic features of ichthyodectiforms, such as the saber-like rays in the pelvic and pectoral fin and possibly the ethmopalatine, a cranial suture that connects the ethmoid bone to the palatine bone. Additionally, Alvarado-Ortega performed phylogenetic analyses based on two datasets, and unlike the first analysis which included all putative ichthyodectiforms, the second analysis excluded Bardackichthys, Jinjuichthys and Mesoclupea from the group.^[2]