Proto or PROTO may refer to:

• Proto-, an English prefix meaning "first"

• Proto (magazine), an American science magazine
• Radio Proto in Cyprus

• Proto (Holly Herndon album), 2019
• Proto (Leo O'Kelly album), 2002
• Proto (band), a progressive rock band from Memphis, Tennessee

• Proto (tools), a tool company (formerly Plomb Tools), now a division of Stanley Black & Decker
• Proto Motors, a South Korean sports car manufacturer and refitter
• Proto Records, a British record company active in the 1980s; see Barry Evangeli
• Proto (paintball), a paintball equipment manufacturing company

• Non-fictional
  • Frank Proto, American composer and bassist
  • Ludovic Proto (born 1965), French boxer
  • Neil Thomas Proto (born 1945), American lawyer, teacher, lecturer, and author
  • Silvio Proto, Belgian goalkeeper
  • Proto (see Protus and Hyacinth), Christian martyr during the persecution of Valerian I
• Fictional
  • Proto, one of the Nereids in Greek mythology
  • Proto (Ghost in the Shell), a fictional character in Masamune Shirow's Ghost in the Shell anime and manga
  • Proto, a more advanced prototype of the Prophetbot from the video game OneShot

• Proto-, the prefix, as used in taxonomy.
• Siebe Gorman Proto, a type of rebreather breathing set
• SEAT Proto, concept cars
• PROTO (fusion reactor)

• All pages with titles beginning with proto
• All pages with titles containing proto
• Protos (disambiguation)