The Invisible Fluid is a 1908 American silent science fiction comedy film produced by the American Mutoscope and Biograph Company of New York, directed by Wallace McCutcheon Sr., and starring Edward Dillon. The short's plot relies extensively on the filming and editing technique of substitution splicing, also known as "stop trick", a special effect that creates the illusion of various characters or objects suddenly vanishing on screen.

Full copies of this trick film, now in the public domain, survive in various formats. Some digital copies are available for viewing on streaming services such as YouTube and at the Internet Archive. Film-stock copies are preserved among the holdings of the Motion Picture, Broadcasting, and Recorded Sound Division at the Library of Congress in Washington, D.C. and in the collection of the British Film Institute in London.