In the Marvel Cinematic Universe, HYDRA made their first appearance in Captain America: The First Avenger as major antagonists in this film together with the film's main antagonist Red Skull, their leader and the founder of HYDRA.
HYDRA returned as antagonists in the sequel of The First Avenger which is Captain America: The Winter Soldier and they hid inside S.H.I.E.L.D. since World War II, where they are led by their high-ranking member, Alexander Pierce, the primary antagonist, and he and HYDRA used the Winter Soldier as an agent and senior henchman.
HYDRA also make a supporting appearance in the 2015 film Avengers: Age of Ultron, where they are led by Baron Wolfgang von Strucker and his right-hand List.
HYDRA also appears in the ABC TV series Marvel's Agents of S.H.I.E.L.D., as a major antagonistic faction, where other HYDRA leaders, including John Garrett, Grant Ward, Daniel Whitehall and Gideon Malick, serve as main antagonists. The third season later reveals HYDRA's true foundation as a cult that worships the ancient Inhuman Hive. HYDRA later appears in the final arc of Season 4 in the digital reality, the Framework, under the leadership of Madame Hydra/Aida. They return in Season 5 under the leadership of its last known leader, General Hale.