A trash bag support which is constituted by two pairs of legs mutually pivoted in a scissor-like fashion, the connecting portions (11c,12c) between two legs support a frame (13), onto which the lip of a trash bag is to be turned, an annular element (15) pivoted to the frame (13) and contoured so as to lock the lip of the bag against the frame (13) and a lid (17) pivoted to the frame (13) in order to close the mouth (14); reversible engagement means are provided for closing the lid (17) on the frame (13), and elastic means for automatically lifting the lid (17) once the engagement means have been disengaged are also provided. The reversible engagement means are constituted by a snap-acting engagement tooth (18), which protrudes from the internal part of the lip (19) of the lid (17) and engages in a lower region a locking abutment (20) formed on a front portion (21) of the frame (13), and rigidly coupled thereto by way of two mutually opposite symmetrical bridges (23), which form the fulcrum of a lever system for the elastic flexing of the front portion (21) so as to disengage the tooth (18) from the abutment (20).