Rugowithius longissimus is a species of pseudoscorpion in the Withiidae family.

It was described in 2015 by Australian arachnologist Mark Harvey.

The specific epithet longissimus (Latin: 'longest') refers to the large size of the species compared to Rugowithius bulbosus.

[1] The species occurs in Far North Queensland in rainforest habitats.

The type locality is 20 km north of Cape Tribulation.