Sotheby's said the winning bid from this week's auction marked the largest amount paid for letters or a manuscript written by a British romantic poet, The Times of London reported Friday.
The letters were won by an anonymous bidder.
Byron reportedly used the 71 pages of handwritten notes to Francis Hodgson, a clergyman, to make written attacks on Christianity and detail a stormy affair with a servant girl.
Sotheby's specialist Gabriel Heaton said the unique subject matter of the letters, many of which are unpublished, offers a rare insight into the influential Romanticism literary figure.
"There has been particular interest in what this unique collection reveals about Byron as a poet, as well as the more sensitive and thoughtful side to a man most frequently recognized as one of history's most notorious Lotharios," Heaton told The Times.