The Decagon House Murders (十角館の殺人, Jukkakukan no Satsujin) is a 1987 Japanese mystery novel, the debut work of author Yukito Ayatsuji.

Borrowing its basic plot structure from Agatha Christie's And Then There Were None (Christie's book is directly referenced by some of the characters at several points), it tells the story of a group of seven university students who travel to a deserted island that was the scene of a grisly mass murder six months earlier, where events soon turn ominous.

The second English-language edition was published in December 2020 by Pushkin Press, and in July 2021 the manga adaptation, illustrated by Hiro Kiyohara, was announced for publication in America.

Seven students, members of their university's mystery club, decide to spend a week-long vacation on Tsunojima Island off the coast of Japan.

Six months earlier the owner of the island was brutally murdered alongside his wife and housekeepers, and the case remains unsolved.