Kiaeropterus is a genus of prehistoric eurypterid classified as part of the Rhenopteridae family.

When it was described in 1892, eurypterid taxonomy had not been firmly established or thoroughly researched and as a result, most new specimens were classified as part of the genus Eurypterus.

[2] When re-studied, the specimen was found to share considerably more features with the Stylonurina than with Eurypterus (which is classified as part of the Eurypterina), for instance its large eyes.

[2] Later studies revealed important similarities with Brachyopterus, including the large eyes converging anteriorly, the lack of a cuticular ornament and simple rectangular appendage podomeres with pronounced ridges.

These similarities prompted it to be classified as a close relative of Brachyopterus, within the family Rhenopteridae.