This study presents a novel wideband absorber for radar cross section (RCS) reduction. Unlike previous absorber designs that use multilayer lossy materials, this study proposes a design based on a planar antenna array that adopts a bowtie dipole structure as the unit cell. The complete design procedure was investigated by using examples for single- and dual-polarized incident wave designs. The measurement results show that the bandwidth of both designs exceeded 81% of 10 dB RCS reduction when the thickness is less than 12% of the free space wavelength at the lowest operating frequency. The high RCS reduction of the proposed absorbers was demonstrated using commercial ground-penetrating radar. Results show that the proposed absorber is invisible to radar.