This paper presents a low profile sierpinski fractal antenna for ultra wide band applications. The proposed antenna is designed by incorporating sierpinski fractals inside a circular ring of width 1mm which improves the impedance band width and radiation efficiency of the antenna. The proffered antenna of dimensions 29×28×1.6 mm3 covering the frequency range of 3.7 to 14.3 GHz with radiation efficiency of 92% is fed by microstrip feed line. The radiation pattern is stable over the operating UWB range. Sierpinski fractal UWB antenna is designed and simulated using High Frequency Structure Simulator (HFSS). © 2015 IEEE.