Hypericum decaisneanum is a species of flowering plant of the St. John's wort family (Hypericaceae) that is found in the Libya.
The placement of H. decaisneanum within Hypericum can be summarized as follows:
Hypericum subg. Hypericum
subsect. Adenosepalum
subsect. Aethiopica
subsect. Caprifolia
Huber-Morathii group
H. decaisneanum