Hydra is a fictional terrorist organization in Marvel Comics, known for its iconic motto, "Hail Hydra." It was created by writer Stan Lee and artist Jack Kirby, first appearing in Strange Tales #135 in 1965. Hydra is often depicted as a secretive group that seeks world domination and is frequently opposed by superheroes like Captain America and The Avengers. The organization is characterized by its use of advanced technology, brainwashing, and a vast network of agents. Its members are often seen wearing distinctive green and white uniforms, and it is led by various villains, including Red Skull and Baron Zemo. Hydra's influence extends across multiple storylines in the Marvel Universe.