What is the name of the detective in 'The Mystery of the Yellow Room'?

The detective in Gaston Leroux’s The Mystery of the Yellow Room is Joseph Rouletabille.

Rouletabille is a young French journalist and amateur detective who investigates the apparent attempted murder of Mathilde Stangerson inside a locked, seemingly inaccessible room. His friend Jean Sainclair narrates the investigation, while Rouletabille competes intellectually with the police detective Frédéric Larsan.

The novel was first published as a serial in L’Illustration from September to November 1907 and appeared in book form in 1908. It is one of the foundational locked-room mysteries, using floor plans, precise physical clues, and apparently impossible disappearances to challenge the reader.

A common mix-up is confusing Rouletabille with Larsan, the official police investigator, or with other famous fictional detectives such as Father Brown and C. Auguste Dupin. Rouletabille is also the protagonist of later Leroux novels, beginning with The Perfume of the Lady in Black.