Downey Jr pictured with his wife Susan
Robert Downey Jr is in final negotiations to play Sherlock Holmes in director Guy Ritchie's movie about the crime fighter, according to a report.
The Iron Man star was introduced to the project through his wife, who works for one of the film's producers, The Hollywood Reporter says.
The film will rival a Columbia Pictures Sherlock Holmes comedy starring Sacha Baron Cohen in the lead role.
Ritchie's Holmes will be less stuffy than previous screen incarnations.
Downey Jr's interest in the project was sparked when he visited producer Joel Silver's Warner-based offices where he was shown Ritchie's version of Holmes.
The film takes its cue from a forthcoming comic book which gives a new slant to Sir Arthur Conan Doyle's classic character, who is portrayed as more adventurous.
Currently given the working title Sherlock Holmes, the film will begin shooting in the autumn for a October 2009 release, according to Warner Bros.
The Columbia Pictures film, meanwhile, also has Will Ferrell on board as Holmes' sidekick Dr Watson.
The 40-year-old Virgin director Judd Apatow is producing the movie, but no director has been announced yet.