Low dislocation density ultraviolet (UV) AlGaNGaN multiple quantum well (MQW) structure was grown using atomic layer deposition (ALD) technique. The AlGaNGaN MQW grown on the sapphire substrate consisted of three GaN QWs and four AlGaN barriers formed by ALD grown AlNGaN superlattices. The as-grown sample showed smooth surface morphology with a root-mean-square roughness value of only 0.35 nm, and no surface cracks were found. The dislocation density was estimated to be as low as 3.3× 107 cm-2. X-ray and transmission electron microscope data showed the MQW had sharp interfaces with good periodicity. The sample had an UV photoluminescence emission at 334 nm (3.71 eV) with a very narrow linewidth of 47 meV at 13 K. The cathodoluminescence image revealed a fairly uniform luminescence pattern at room temperature. The AlGaNGaN MQW grown by ALD technique should be useful for providing high crystalline quality for fabrication of various optical devices.