Journey Under the Midnight Sun (白夜行, Byakuyakō) (also published in English as Under the Midnight Sun) is a mystery novel written by Keigo Higashino, first serialized in the monthly novel magazine Subaru from Shueisha from January 1997 to January 1999. The entire volume was published in August 1999 and became a bestseller.

During the serialization, the novel was at first written as a series of short stories representing chronological snapshots of the overall plot line. Higashino modified its structure to make it a single coherent story before publishing it as a single volume. As of November 2005 the book had sold 550,000 copies. However, its sales quickly picked up after the first episode of the adapted TV series was aired. By January 2006 its sales had broken a million. Its sales exceeded 2 million in December 2010.

The novel attracted adaptations, including a stage drama in 2005, a Japanese TV series in 2006, a Korean motion picture in 2009, and a Japanese motion picture in 2010.