A two-dimensional horn imaging array has been demonstrated at 242 GHz. In this configuration, a dipole is suspended in a pyramidal horn on a 1-μm silicon-oxynitride membrane. This approach leaves room for low-frequency lines and processing electronics. Pattern measurements agree well with theory, and show no sidelobes and 3-dB beamwidth of 35° and 46° for the E and H planes respectively. Possible application areas include superconducting tunnel-junction receivers for radio astronomy and imaging arrays for plasma diagnostics and radiometry.