New data on distribution, ecology and cytology of the Azorean endemic Asplenium azoricum are presented. Hybrids involving this species are recorded for the first time. The extremely rare, natural hybrid A. azoricum × A. scolopendrium is described as A. ×santamariae. It has been found at a single location on Santa Maria Island and is presumed to be triploid. A more frequent natural hybrid A. azoricum × A. onopteris, found at seven locations on the same island, is also new to science and is described here as A. ×diasii. It is confirmed cytologically as triploid with two genomes from A. azoricum and one from A. onopteris. Asplenium ×diasii and an experimental hybrid show that A. azoricum is an allotetraploid species. The parentage and directionality of hybridization for both hybrid taxa have been established using uniparentally inherited plastid genome markers.