"I Wrote the Book" is a song by American country music singer Morgan Wallen, released on January 31, 2023 from the second sampler of his third studio album One Thing at a Time. It was written by Morgan Wallen, Michael Hardy, and Cameron Montgomery, and produced by Joey Moi, Cameron Montgomery and Jacob Durrett. The song is about "reconnection with the Bible".
Wallen teased of the new song on his social media accounts on January 20, 2023. In January 30, 2023, Wallen revealed One Thing at a Time would be released at March 3, 2023, the same day Wallen released a sampler included "Last Night", "Everything I Love", and "I Wrote the Book".
Billy Duke of website Taste of Country referred to the song as "the '80s style guitar Wallen relies on during "Everything I Love" returns here, paired with a drum track and power melody".
"I Wrote the Book" debuted at number 58 on the Billboard Hot 100 on the chart dated February 11, 2023, jumping to number 38 the following week.
Following the release of One Thing at a Time, it ascended from number 64 to number 18 on the Billboard Hot 100 dated March 18, 2023.