# look out for number one

idiom

Source: https://englishreference.com/idiom/look-out-for-number-one
Updated: 2026-08-10

## Meaning

To act in one's own interests; to act in a manner advantageous primarily to oneself.

## Examples

- He always looks out for number one in every situation.
- In this competitive industry, you must look out for number one if you want to succeed.
- She realized that her colleagues were only looking out for number one, so she stopped sharing her best ideas with them.

## Origin

Attested since the 1830s at the latest, the phrase is a compound of *look out for* and *number one*, the latter functioning as a substitute for oneself.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.