The "venturi fan" comprises a series of "half-venturi" shaped profiles incorporated into the periphery of a cylindrical fan, for use with a cylindrical heat sink. In one embodiment, the half-venturis are open, in another the half-venturis are enclosed so that the outer surface of the fan is smooth so that it is not a hazard to intruding fingers and the like. A leading edge deflector keeps hot compressed air in front of the venturi out of the heat sink fins.