We present a compact geodesic H-plane horn antenna for point-to-point communications at W-band. The horn has a curved height profile with truncated corners to reduce phase errors and achieve high gain and aperture efficiency. The laser powder-bed fusion additive manufacturing technique is applied to fabricate the horn antenna in a monolithic manner. The resulting prototype has a weight of only 14 g including the flange part. In the operating band from 75 to 110 GHz, the measured reflection coefficient is below -15 dB in almost the entire band and agrees well with the expectations from the simulation. The simulation shows a realized gain of 20 dBi with an aperture efficiency of 80% and a total efficiency of nearly 80%.