Users in the south and south-east of England started experiencing the most difficulty.
Both social media sites are displaying error messages once those in these areas attempt to use them.
It reads: "Oops... Something went wrong. We're working on getting it fixed as soon as we can."
It's unclear what has caused the mayhem or for how long it'll remain.
One man posted: "Facebook & Instagram are down, which means people are quickly remembering Twitter exists.
"It’s like running out of your favorite wine, then you remember those loose Bud Lite bottles waaaaay in the back of your fridge."
Another wrote: "Facebook is down it looks like. People are actually going to have to talk to each other!"
A spokesman for Facebook said: "There’s a global severe issue at the moment. Our engineers are investigating urgently, will let you know when we hear more."
But when Facebook crashed in December, users across the UK panicked and grew concerned the social media had been hacked.
Reports then suggested 44% of UK users had a total blackout. SHARE THIS STORY USING ANY OF THE BUTTON BELOW ⬇ PLACE YOUR TEXT ADVERT BELOW ⬇⬇⬇