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

It was described in 1987 by Australian arachnologist Mark Harvey.

The specific epithet leo (Latin: 'lion') refers both to the type locality and the relatively large size of the species.

[1] The species occurs in south-west Western Australia.

The type locality is Lion Island, near Esperance in the Recherche Archipelago, where the pseudoscorpions were found beneath granite slabs.