A Beautiful Lie is the second studio album by American rock band Thirty Seconds to Mars, released on August 30, 2005 through Virgin Records. It was produced by Josh Abraham.

A Beautiful Lie differs notably from the band's self-titled debut album, both musically and lyrically. Whereas the eponymous concept album's lyrics focus on human struggle and astronomical themes, A Beautiful Lie's lyrics are "personal and less cerebral". It is the first to feature guitarist Tomo Miličević and the only one to feature bassist Matt Wachter, who left the band in 2007. The album produced four singles, "Attack", "The Kill", "From Yesterday", and "A Beautiful Lie"; of which three of those four singles managed to chart within the top 30 on the US Modern Rock chart, with "The Kill" and "From Yesterday" entering the top three.

A Beautiful Lie received positive reviews from music critics, many praising the album for diverging from the sound of the band's previous work. It has been stylistically described as post-hardcore, hard rock, alternative rock and emo. The success of the album had helped the band receive accolades for their singles such as "The Kill" and "From Yesterday".