Eckhart gained wide recognition as George in Steven Soderbergh's critically acclaimed film Erin Brockovich (2000), and, in 2006, he received a Golden Globe nomination for his portrayal of Nick Naylor in Thank You for Smoking. Another mainstream breakout occurred in 2008 when he starred in the blockbuster Batman film The Dark Knight as District Attorney Harvey Dent. Other key roles include The Pledge (2001), The Core (2003), Paycheck (2003), Rabbit Hole (2010), Battle: Los Angeles (2011), Olympus Has Fallen (2013) and its sequel London Has Fallen (2016), I, Frankenstein (2014), and Sully (2016).
Eckhart portrayed the comic book character Harvey Dent in Christopher Nolan's The Dark Knight, the sequel to the 2005 film Batman Begins. Nolan's decision to cast Eckhart was based on his portrayal of corrupt characters in the films In the Company of Men, The Black Dahlia, and Thank You For Smoking. He noted in his depiction of the character that "[he] is still true to himself. He's a crime fighter, he's not killing good people. He's not a bad guy, not purely", while admitting "I'm interested in good guys gone wrong. The Dark Knight was a big financial and critical success, setting a new opening weekend box office record for North America. With revenue of $1 billion worldwide, it became the fourth highest-grossing film of all time, and the highest-grossing film of Eckhart's career. Roger Ebert opined that Eckhart did an "especially good job" as his character in the feature, while Premiere magazine also enjoyed his performance, noting that he "makes you believe in his ill-fated ambition ... of morphing into the conniving Two-Face."