Synsphyronus amplissimus is a species of pseudoscorpion in the Garypidae family. It is endemic to Australia. It was described in 1987 by Australian arachnologist Mark Harvey. The specific epithet amplissimus (Latin: 'largest') refers to its size relative to its congeners.
The body length of females is 5.6âÂÂ5.9 mm. Colouration is reddish-brown.
The species occurs in the southern Northern Territory. The type locality is Mount Conner.
The pseudoscorpions are terrestrial predators.