Pope Francis mistakenly used a foul word in his Sunday address to the masses, with the video of his error going viral on the social media.

Pope Francis, speaking in Italian, used the word “cazzo” (which in Italian is slang for the male sexual organ but is also used as an expression of anger, similar to the "f.ck" expression in the English language) instead of “caso”, quickly correcting himself without as much of a smile or a blink.

But his mistake was quickly picked up and has been doing the rounds on the social media ever since, attracting thousands of viewers.