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

It was described in 1987 by Australian arachnologist Mark Harvey.

The specific epithet lathrius comes from the Greek lathrios ('hidden' or 'stealthy'), referring to the superficial similarity this species has with S. niger, with which it has been confused.

[1] The species occurs in Western Australia.

The type locality is 98 km east-north-east of Norseman, where the holotype was found beneath stones.