This disclosure describes a radio frequency identification (RFID) tag that includes a three-dimensional (3D) loop antenna. The 3D loop antenna includes a first conductive portion having a length and width that substantially exceed a thickness. The length and width of the first conductive portion substantially lie in a first plane. The 3D loop antenna includes a second conductive portion having a length and width that substantially exceed a thickness. The length and width of the second conductive portion substantially lie in a second plane that is substantially parallel to the first plane. An RFID circuit electrically connected to the loop antenna excites a current through the first and second conductive portions in a current loop that lies in a third plane that is not substantially parallel to the first and second planes. In some instances the third plane may be substantially perpendicular to the first and second planes.