Asplenium oblongifolium is a native species of fern from New Zealand.

[1] A. oblongifolium is found on the North, South, Chatham and Kermadec Islands, and is found from the coast to the mountains.

[2] A global phylogeny of Asplenium published in 2020 divided the genus into eleven clades,[3] which were given informal names pending further taxonomic study.

A. oblongifolium belongs to the "Neottopteris clade", members of which generally have somewhat leathery leaf tissue.

It formed a clade with A. northlandicum, A. obliquum, and A. obtusatum.