Synsphyronus tenuis is a species of pseudoscorpion in the Garypidae family.

It was described in 2022 by Australian arachnologist Mark Harvey.

The specific epithet tenuis (Latin: 'thin') refers to the species’ extremely slender appendages.

[1] The species occurs in south-west Western Australia in the Geraldton Sandplains bioregion.

The type locality is Kalbarri National Park, where the pseudoscorpions were found beneath sandstone rocks.