In this paper, A novel compact wideband aperture-coupled antenna with high polarization purity and high front-to-back (F/B) ratio is proposed for 5 GHz WLAN applications. The high polarization purity is attributed to the aperture-coupled feeding mechanism, and with the aid of a quarter-wavelength choke, the F/B ratio can be increased. Simulated results show that the proposed antenna occupying a compact size of 0.46λ0×0.46λ0×0.24λ0 (λ0 is the lower frequency wavelength) achieves a bandwidth of 27% for 10-dB return loss ranging from 4.66 to 6.12 GHz. The F/B ratio is above 22 dB and the cross-polarizations in both E- and H- planes are lower than −44 dB within the operating bandwidth.