N-polar Ⅲ-nitride heterostructures and devices have been a subject of intense investigation recently, as the inverted polarization fields provide unique advantages over the metal-polar devices. From the molecular beam epitaxy (MBE) growth point of view, however, obtaining p-type conductivity in Mg-doped N-polar heterostructures is challenging. This is because unintentional oxygen donor incorporation is higher but Mg incorporation is lower for N-polar growth compared to the metal-polar counterpart, both by roughly an order of magnitude. Polarization-induced doping provides an alternate route to obtain p-type conductivity. In this work, we report the observation of polarization-induced two-dimensional hole gases (2DHGs) in N-polar AlGaN/GaN heterostructures grown by plasma-assisted MBE. AlGaN/GaN heterostructures were grown on N-polar semi-insulating GaN bulk substrates. The existence of 2DHGs in these heterostructures is confirmed by the stable p-type conductivity and high hole mobilities observed in temperature dependent Hall effect measurements. Through transport analysis, we have shown that acoustic piezoelectric scattering has significant influence on the mobility of 2DHGs with relatively low density (< 2×1013 cm-2).