The World's heaviest snake which weighs at a staggering 550 lbs is the Eunectes murinus.
The species of snake Eunectes murinus is also known as the green anaconda.
The Eunectes murinus can grow from 17 feet long and even 30 feet long.
So as of now that would be the world's largest and heaviest weighing snake in the world today unless some other bigger snake comes along which I would be really surprised if one did.