The original Avengers lineup in the Marvel Cinematic Universe (MCU) consists of Iron Man (Tony Stark), Thor, Captain America (Steve Rogers), the Hulk (Bruce Banner), Black Widow (Natasha Romanoff), and Hawkeye (Clint Barton). Of these original Avengers, Hawkeye (Clint Barton), portrayed by Jeremy Renner, was not featured in the first MCU film, "Iron Man," released in 2008.
Hawkeye made his first appearance in the MCU in the film "Thor," which was released in 2011. He had a small but significant cameo in that movie before becoming a full-fledged member of the Avengers team in "The Avengers" (2012).