Cystopteris laurentiana, commonly called Laurentian bladderfern or St. Lawrence bladderfern, is a species of fern in the family Cystopteridaceae.

[1] It is native to eastern North America, primarily in the Great Lakes-St. Lawrence lowlands, but there are also scattered occurrences in New England and Atlantic Canada.

[2] It grows on cliffs composed of calcareous rocks, such as limestone, dolostone and diabase.

[2][3][4] Cystopteris laurentiana is a fertile allohexaploid hybrid between C. bulbifera (bulblet fern) and C. fragilis (fragile fern).

[2] The scientific name is therefore sometimes written as C. × laurentiana, which denotes hybrid origin.