Justin Bieber reached the limit on what he'll do to promote his new album -- and the meltdown happened live on the air during a radio interview in Spain.
The video is perplexing ... the hosts offer Justin a chance to "break the internet" with some hijinks they've set up with YouTubers who have "hundreds of millions" of followers.
Biebs seems game for whatever they're cooking, but then abruptly stands up and peaces out. According to one report in Spain ... JB said he had to go to the bathroom and never returned.
It's unclear what pushed Justin to his breaking point, but he went full hasta luego.