What is the name of the substance that turned Steve Rogers into Captain America?

The substance that transformed Steve Rogers into Captain America is the Super Soldier Serum.

In the MCU, scientist Abraham Erskine injects Steve Rogers with the serum as part of the wartime Super Soldier experiment. Rogers is then exposed to vita-rays, which stabilize and amplify the treatment. The procedure transforms his frail body into one with extraordinary strength, speed, endurance, reflexes, durability, and accelerated healing.

The serum does not create Steve’s moral character. Erskine chooses Rogers because he believes the experiment should enhance a good person rather than give power to someone already motivated by cruelty. That idea becomes central to Captain America’s story and explains why the serum is not treated as a simple weapon.

The experiment is also dangerous and difficult to reproduce. Erskine is killed soon afterward, and the original formula is lost. Later attempts produce imperfect or unstable versions, including the serum used by other super-soldiers. Pym Particles belong to Ant-Man’s technology, while vibranium is the metal used for Captain America’s shield.