The Great Mouse Detective (released as Basil the Great Mouse Detective in some countries and The Adventures of the Great Mouse Detective during its 1992 re-release) is a 1986 American animated mystery adventure film produced by Walt Disney Feature Animation and released by Walt Disney Pictures. Based on the children's book series Basil of Baker Street by Eve Titus and Paul Galdone, the film is written and directed by John Musker, Dave Michener, Ron Clements, and Burny Mattinson in their feature directorial debuts. Featuring the voices of Vincent Price, Barrie Ingham, Val Bettin, Susanne Pollatschek, Candy Candido, Diana Chesney, Eve Brenner, and Alan Young, the plot follows a mouse detective who undertakes to help a young mouse find and save her father from the criminal mastermind Professor Ratigan.

The Great Mouse Detective draws heavily on the tradition of Sherlock Holmes with a heroic mouse who consciously emulates the detective. Titus named the main character after actor Basil Rathbone, who is best remembered for playing Holmes in film (and whose voice, sampled from a 1966 reading of "The Red-Headed League" was the voice of Holmes in this film, 19 years after his death). Sherlock Holmes also mentions "Basil" as one of his aliases in the Arthur Conan Doyle story "The Adventure of Black Peter".

The Great Mouse Detective was released to theaters on July 2, 1986, to positive reviews from critics and financial success, in sharp contrast to the box office underperformance of Disney's previous animated feature film, The Black Cauldron (1985). The film's timely success has been credited with keeping Walt Disney Animation going after the previous film's failure by renewing upper management's confidence in the department, thus setting the stage for the Disney Renaissance when feature animated films would become the corporation's most lucrative and prestigious product.