In this letter, we propose a generalized coprime planar array (GCPA) geometry for 2-D direction of arrival (DOA) estimation, where two rectangular uniform planar subarrays are used. The proposed geometry allows a more flexible array layout and extends the array aperture to achieve a great performance improvement. We verify that GCPA can obtain a higher degree of freedom (DOF) than square coprime planar array and we derive the principle for array layout of GCPA to obtain the maximum DOF. The superiority of GCPA are revealed by numerical simulations with the classical DOA methods.