In this study, a novel wideband slant-polarized antenna consisting of a double-ridged horn antenna and a slant polarizer is proposed. The designed slant polarizer is placed in front of the designed double-ridged horn antenna. In this way, linear polarization of the traditional double-ridged horn antenna is changed to slant polarization over a wide frequency range. This design provides a double-ridged horn antenna to be capable of transmitting and receiving whole linearly and circularly polarized signals over a wide frequency range without affecting the antenna characteristics. It also provides the ability to simultaneously radiate vertical and horizontal polarization components. The frequency range of the proposed double-ridged horn antenna with the slant polarizer is 6-18 GHz with 12 dBi typical gain. The performance of the proposed design is examined with simulations and verified with the measurements. The measurement results are in very good agreement with the simulation results.