Its a coconut crab, (AKA Robber Crab plus a whole host of other names) the largest of the land arthropods. They get be about 9 pounds, 16 inches long in the body with a leg span of about 3 feet. They are also fairly strong, able to lift around 64 pounds with those powerful front claws of theirs.

I will say that the picture is pretty impressive, but you have to keep in mind that there isn't a clear indicator to compare for scale.

Old records have claimed they can get over 30 pounds with a leg span over 6 feet, but most scientists seem to feel that the current size listing is pretty much the maximum of what a land creature supported by an exoskeleton in today's environment could possibly obtain.