Abstract: A drill drive for a drilling rig includes a motor, by which a drive shaft is rotationally driven which is supported in a rotatable manner in a housing with a bearing arrangement having at least a radial bearing, a first axial bearing and a second axial bearing. On the first axial bearing a first force measuring device is arranged for determining a first axial force on the first axial bearing and on the second axial bearing a second force measuring device is arranged for determining a second axial force on the second axial bearing. A drilling rig, in particular for oil or gas drilling, with a drill mast, along which a drill string with a drilling tool is arranged, wherein on the drill mast a drill drive according to the invention is supported in a displaceable manner for rotationally driving the drill string.