123456 is a number. It can refer to:
- 123456, a common example of poor password strength
- "123456", a song by Fitz and the Tantrums from the album All the Feels
- Braille pattern dots-123456, a braille cell
- 123456, or 123 456, a typical example of specifying a six-digit vehicle license plate number, for instance, as with United States license plate designs and serial formats
- The first six positive Arabic numerals