In this paper low profile, low cost, and highly efficient antenna for ultrawideband (UWB) applications is presented. A novel shape of recta-tri substrate integrated waveguide antenna is designed to achieve a wideband response and high efficiency. The proposed antenna is printed on FR4 substrate with a thickness of 1.6 mm. The overall antenna dimension is 30 × 35 mm 2 . The frequency of the antenna bandwidth ranges from 3.64 to 14.17 GHz with a peak gain of 7.7 dB. The field distribution of the proposed antenna is observed.The fabricated antenna results are tested and compared, which well agree with the simulated results. The proposed antenna is suitable for Wi-Fi, ISM, and UWB applications.