A1 or A-1 can mean:
- A1, a symbol indicating shipbuilding quality, originally in the shipping list at Lloyds of London.
- The highest degree of excellence (from the meaning in shipping).
- A1, a British boy band.
- A1 , milk containing a protein supposed by some to cause heart disease.
- A1, the primary auditory cortex, that is, the part of the brain processing hearing.
- A1, a brand of steak sauce .
- A1, a German rocket design from the 1930s.
- A1, an international standard paper size (594×841 mm), defined in ISO 216.
- HMS A1, an A-class submarine of the Royal Navy.
- USS A-1, two vessels of the United States Navy.
- The A-1 Skyraider, a USAF single-seat attack bomber.
There are several roads and freeways named A1:
