A device for feeding yarns for knitting machines comprising a supporting element arranged on the inner side of the machine bed which supports a set of yarn guides arranged side-by-side. Each of the yarn guides has a passage for at least one yarn to be fed to the needles of the machine arranged in the bed and the supporting element, for each of the yarn guides, supports an element for clamping and cutting the yarn dispensed by the corresponding yarn guide. A first actuator for the yarn guides is provided for the passage of the yarn guides from an inactive position to an active position, and a second actuator is provided for actuating the clamping and cutting elements. The first actuator comprises individual actuators actuated to produce passage of each of the yarn guides from the inactive position to the active position or vice versa.