A novel phase corrected substrate integrated waveguide (SIW) H-plane horn antenna with embedded metal-via arrays is presented. The SIW horn is divided into four subhorns by three metal-via arrays inside the horn. A uniform phase distribution of EM field across the horn aperture is achieved by adjusting the lengths and positions of the metal-via arrays. The proposed horn antenna has a compact profile, and its simulated gain is 7.50 dBi at 35.5 GHz, whereas the simulated gain of a traditional horn antenna without the metal-via arrays is 6.38 dBi. When measured, the gain of the proposed horn antenna is 7.87 dBi at 35.5 GHz, whereas the gain of the traditional horn antenna is 5.58 dBi. Good agreement between the simulated and the measured results is obtained.