Out of the blue
/ˌaʊt əv ðə ˈbluː/neutral, informalUK · US · AU · IE · CA
What does “Out of the blue” mean?
Out of the blue means something happens completely unexpectedly and without any warning.
If something happens out of the blue, it arrives with no warning. You do not expect it, and nothing prepared you for it. For example, a person might quit their job or receive a sudden letter.
This is a very common phrase in everyday English. It is friendly and natural to use when you want to share a surprise with someone.
When do people say it?
People use this phrase to describe news, visits, or events that take them by surprise.
“An old school friend called me out of the blue yesterday.”
Is it formal or informal?
Register: neutral, informal. It is most at home in both everyday conversation and professional writing. Most common in UK and US and AU and IE and CA.
Where does it come from?
It comes from the image of a lightning bolt striking from a clear blue sky. Over time, people shortened the older phrase "a bolt out of the blue."
Origin confidence: Well documented
How do you say “Out of the blue” in other languages?
Last reviewed 2026-09-11