Four Flies on Grey Velvet (Italian: 4 mosche di velluto grigio) is a 1971 giallo film written and directed by Dario Argento.

The film concerns Roberto Tobias (Michael Brandon), who accidentally kills a man and is then tormented by someone who witnessed the event.

Holding Roberto at gunpoint, Nina explains that her physically and mentally abusive stepfather committed her to the Villa Rapidi asylum.

Some of the earlier cast considerations for the main role Roberto Tobias were Terence Stamp, Michael York and even some members of the Beatles.

However, he criticized the plot as "not only old but farfetched" and the dialogue as "banal", and went on to say that "[a]ll that circuitous teasing and those red herrings don't produce a shred of real evidence to nibble on.

"[6] Roger Ebert gave the film a mixed review of two-and-a-half stars out of four, deeming it a "badly dubbed and incoherent murder thriller" with "a conclusion that's so arbitrary we feel tricked."

"[7] Gene Siskel of the Chicago Tribune gave the film one star out of four and wrote, "Argento's script contains more red herrings than the Cape Cod Room.

Each time evidence overwhelmingly points to a possible threat to our bushy-haired hero that person is bumped off and the guessing game begins anew.

"[10] David Pirie of the Monthly Film Bulletin noted it being "full of slick visual conceits and glossy set-pieces, this is clearly Argento's most expensive and ambitious thriller yet" while stating its still as "flat and predictable as that of the most meager Italian 'B' feature.

"[1] Leonard Maltin's Movie Guide gave the film two stars out of four and opined it was an "[u]nabsorbing psychological murder-mystery with performers who walk through their roles in a very disinterested fashion.

"[12] AllMovie gave the film a positive review, calling it "an unfortunately overlooked and hard-to-find choice nugget in his [Argento's] oeuvre".

[13] It was not until early 2009 that the film was made available to home video audiences in a legitimate version, both domestically or internationally, with the exception of the long out-of-print obscure French VHS.

The disc contains an uncut, completely remastered print of this "lost" film, featuring theatrical trailers, the English language opening and ending credits and an extensive photo gallery.

[14] To celebrate the film's 40th anniversary and to mark 20 years since it was thought to be lost, Shameless Screen Entertainment released it on Blu-ray and DVD in the UK on 30 January 2012.