This paper presents a frequency reconfigurable monopole antenna that uses a switchable defected ground structure to switch between two bands – UWB (2.6 GHz to 10 GHz) and sub-6 GHz from 2.6 GHz to 5.6 GHz. Two slots are created in the partial ground plane of the monopole antenna that act as defected ground structure resonators of length λg/2. The DGS alters the current distribution of the antenna and thereby causes a change in the operating bandwidth of the monopole. Two p-i-n diodes are used to control the surface current path along the DGS resonators. The radiation characteristics show good efficiency and gain in passband and reduction in gain and efficiency in the stopband indicating good stopband characteristics. The antenna is suitable for use in UWB and sub-6 GHz 5G applications.