M23, M.23 or M-23 may refer to:

• HMS M23, a Royal Navy M15-class monitor
• M23 chemical mine, a US landmine
• March 23 Movement (M23), a rebel group operating in the Democratic Republic of the Congo
  • M23 rebellion (2012–2013)
  • M23 campaign (2022–present)
• Sako M23, a Finnish family of assault and battle rifles

• M23 motorway, a motorway in England
• M-23 (Michigan highway), a highway designation formerly used in Michigan
• Highway M23 (Ukraine)
• M23 (Cape Town), a Metropolitan Route in Cape Town, South Africa
• M23 (Pretoria), a Metropolitan Route in Pretoria, South Africa
• Federal Highway (Australia), part of which is given the designation "M23"

• M23 (New York City bus), a New York City Bus route in Manhattan
• BFW M.23, two-seater sports plane
• The Mathieu group M23 in the mathematical field of group theory
• m23 software distribution system, a Linux software distribution and management system
• McLaren M23, a race car
• Messier 23 (M23), an open star cluster in the constellation Sagittarius
• M23 derby, a football association match between Brighton and Hove Albion and Crystal Palace
• Samsung Galaxy M23 5G, an Android-based smartphone