A wideband on-chip millimeter-wave patch antenna in 0.18 μm CMOS with a low-resistivity (10 Ωcenterdotbm) silicon substrate is presented. The wideband is achieved by reducing the Q factor and exciting the high-order radiation modes with size optimization. The antenna uses an on-chip top layer metal as the patch and a probe station as the ground plane. The on-chip ground plane is connected to the probe station using the inner connection structure of the probe station for better performance. The simulated S11 is less than ?10 dB over 46–95 GHz, which is well matched with the measured results over the available 40–67 GHz frequency range from our measurement equipment. A maximum gain of ?5.55 dBi with 4% radiation efficiency at a 60 GHz point is also achieved based on Ansoft HFSS simulation. Compared with the current state-of-the-art devices, the presented antenna achieves a wider bandwidth and could be used in wideband millimeter-wave communication and image applications.