S.H.I.E.L.D. (Originally an acronym for Supreme Headquarters, International Espionage, Law Enforcement Division, subsequently changed to Strategic Hazard Intervention, Espionage and Logistics Directorate) is a fictional intelligence agency in the Marvel Universe.

Usually led by Colonel Nick Fury as Executive Director, this organization operates as a covert agency of the United States government with vast technological resources at their disposal. Most famously as their headquarters for a long period, was the Helicarrier, a massive flying aircraft carrier that was kept airborne at all times and among other things, contained a squadron of jet fighters and also housed an ICBM. In addition, they maintain strong ties to the superhero community and often call upon their aid for particular missions, especially Captain America.

S.H.I.E.L.D. was introduced in Strange Tales #135 (1965), in which Colonel Fury (formerly the lead character of Marvel Comics' World War II series Sgt. Fury and His Howling Commandoes) was appointed head of the organisation. Several characters from the Sgt. Fury series reappeared as agents of S.H.I.E.L.D., most notably Thaddeus "Dum-Dum" Dugan, Fury's bowler hat-wearing aide-de-camp. Their most persistent enemy was HYDRA, a criminal organization founded by Baron Wolfgang von Strucker whose name is taken from the mythical monster to symbolize its ability to grow stronger the more it is wounded.

Perhaps not coincidentally, Strange Tales #135 came out during a trend for action series about secret international intelligence agencies with catchy acronyms led by television's The Man from U.N.C.L.E..