The Avengers are Earth's Mightiest Heroes. Countless comics have made based off of them, as well as multiple live-action blockbuster movies. This website will look at the origins of each of the Avengers. However, this will only include the original Avengers in the Marvel Cinematic Universe. There are 6: Iron Man, Captain America, Black Widow, Thor, Hawkeye, and The Hulk.
Anthony Edward "Tony" Stark is the son of Howard and Maria Stark. He is a billionaire and an inventor. On a trip to Afghanistan, Tony is caught in an ambush which results in a piece of shrapnel being cast into his chest, reaching towards his heart. Stark is capture by the Ten Rings and has an electromagnet built for him to keep the shrapnel from reaching his heart by Ho Yinsen. Stark has to build a missile in exchange for his freedom, but he, with the help of Yinsen, instead builds a powered suit of armor. After escaping, Tony was rescued and brought home where he began to work on more suits, becoming the superhero Iron Man. Stark would later join the Avengers in order to take down Loki.
Steven Grant Rogers was a young man who was desperate to serve in the U.S. military, but was rejected multiple times as he was extremely unfit. Rogers later volunteered for a secret project and was injected with a super .soldier serum, which healed his body and gave him intense strength. This led him to becoming the character "Captain America" for war bonds and later an actual superhero with the same name. Years later, he would join the Avengers under Director Nick Fury.
Natasha Romanoff was born in the Soviet Union as Natalia Alianovna Romanova. She was orphaned as a child and was soon taken in by the Soviet Union Intelligence. After the Second World War, Romanoff was recruited in the Black Widow Program and trained in the Red Room. Sometime later, after realizing what she'd done over the years, and desperate to get red off her ledger, Natasha joined S.H.I.E.L.D. and later the Avengers under Director Nick Fury.
Thor is the son of Odin the Allfather and is the Norse god of thunder. Thor is heir to the throne of Asgard, but when his bold and cocky behavior reignites a feud between Asgard and Jotunheim, he is stripped of his title and power and banished to Earth. During his time there, Thor learns how to improve himself and is proved redeemable to his father, which grants him his powers again. In the future, Thor joins the Avengers in order to stop his younger brother Loki, the god of mischief.
Clinton Francis "Clint" Barton was born in 1994 to Edith Barton. During time at a fair with his mother, Clint learned how to improve his aim and concentration. The two did not have much money, so Edith decided to steal from a gas station register. However, it failed and Edith was arrested by police, leaving Clint alone. Through the years, Clint became more proficient in marksmanship, mainly with a bow and arrow. In 2004, he was hand-picked by Nick Fury to join S.H.I.E.L.D., where he met his future wife, Laura. Fury set up protection for the both of them, even setting up a farmhouse for the Bartons and their children. Hawkeye was sent on many missions, two separate missions involving Black Widow and Thor. He later joined the Avengers to take down Loki after he had been mind-controlled by the trickster god.
Doctor Robert Bruce Banner is a renowned scientist and his respected for his work in biochemistry, nuclear physics, and gamma radiation. Banner was chosen by Thaddeus Ross to recreate the Super Soldier Serum that created Captain America. During the experiment, however, Banner was exposed to dangerous amounts of gamma radiation. This resulted in Banner becoming a rage-filled creature known as the Hulk when he became angered or provoked. Banner hid from the U.S. Army for years until recruited by Natasha Romanoff to join the Avengers to take down Loki and to track down the Tesseract.