03 may refer to:

• The year 2003, or any year ending with 03
• The month of March
• 3 (number)

Music

• 03 (Twelve album), 2007
• 03 (Urban Zakapa album), 2013

Other uses

• 03 numbers, a non-geographic telephone number range in the UK
• The telephone area code for the South Island of New Zealand.
• The number of the French department Allier
• The occupational field designator for U.S. Marine Corps Infantry
• Tokyo Metro 03 series

See also

• O3 (disambiguation)
• 3 (disambiguation)