This article presents 16-52-GHz multiband transmit and receive phased arrays designed to support multistandard 5G communications. The 64-element arrays are built using <inline-formula> <tex-math notation="LaTeX">16\,\times \, 1 </tex-math></inline-formula> linear arrays, and each has four <inline-formula> <tex-math notation="LaTeX">4\,\times \, 1 </tex-math></inline-formula> beamformer chips on a six-layer printed circuit board (PCB) with a Wilkinson combiner/divider network and tapered slot antennas. The wideband beamformer chips are designed in a SiGe BiCMOS process and use the RF beamforming architecture. The arrays have ±60° scanning capability in the azimuth plane and ±30° in the elevation plane with low sidelobes. The 64-element Tx array achieves an effective isotropic radiated power (EIRP) of 50-51.7 and 47.6-49 dBm at <inline-formula> <tex-math notation="LaTeX">P_{\mathrm{ sat}} </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">P_{1\,{\mathrm{ dB}}} </tex-math></inline-formula>, respectively, at 24.5-48 GHz. The 5G-NR-compliant waveforms with 400 MHz and up to 256-quadrature amplitude modulation (QAM) are transmitted with <2.98% EVMrms and 34-36 dBm average EIRP. Single-carrier (SC) 400-MHz 64-QAM waveforms are also transmitted achieving <3% EVMrms with 39-40.3 dBm average EIRP and 2.4 Gb/s data rate. The 64-element Rx array achieves a system NF of 5.3-6.9 dB and a measured <inline-formula> <tex-math notation="LaTeX">G/T </tex-math></inline-formula> of −19.3 to −14.4 dB (with <inline-formula> <tex-math notation="LaTeX">{T} _{\mathrm{ ant}} = 295 </tex-math></inline-formula> K) at 20-50 GHz, and < 2.6% error vector magnitude (EVM) performance when tested with 400-MHz 256-QAM 5G-NR-complaint packets. To the author's knowledge, this work achieves the highest bandwidth Tx and Rx phased array systems suitable for multiband 5G operation.