001, O01, or OO1 may refer to:

• 1 (number), a number, a numeral
• 001, fictional British agent, see 00 Agent
• 001, former emergency telephone number for the Norwegian fire brigade (until 1986)
• AM-RB 001, the code-name for the Aston Martin Valkyrie sports car
• 1992 OO1, the asteroid 10111 Fresnel
• 1997 OO1, the asteroid 9987 Peano
• O01, an allele, see ABO
• O01 Heussler Hamburg Heliport, see list of airports in New York
• 001, also known as the Princess of Klaxosaurs, is a character and the central antagonist from DARLING in the FRANXX.
• 001, the code for the World in the UN M49 standard for area codes
• Player 001, a character from the South Korean survival drama Squid Game.
• Zeekr 001, an electric vehicle produced by Geely