Pachycorioolithus is an oogenus of small, thin-shelled fossil egg from the early Cretaceous in China.

[1] Based on its unique characteristics, Lawver et al. (2016) assigned Pachycorioolithus to its own monotypic oofamily, Pachycorioolithidae.

[1] The only known P. jinyunensis specimen was discovered in a quarry near Shuhong, a town in Jinyun County in Zhejiang.

[1] Pachycorioolithus was first described in 2016 by a team of paleontologists consisting of Daniel R. Lawver and Frankie D. Jackson of the Montana State University, Jin Xingsheng of the Zhejiang Museum of Natural History, and Wang Qiongying of the Jinyun Museum.

They gave it the name Pachycorioolithus jinyunensis, from the Greek "pachys" (thick) and "corys" (helmet), a reference to its thick outer layer, combined with "oolithus", the standard suffix for oogenus names, meaning "stone egg".