This letter presents the design and characterization of a Ka-band low-noise-amplifier (LNA) monolithic microwave integrated circuit (MMIC) implemented on a 70-nm gallium nitride (GaN)-on-SiC high-electron-mobility transistor (HEMT) process. The three-stage LNA combines microstrip and coplanar technologies to minimize the losses before the first transistor and shows an average small-signal gain of 25 ± 2.5 dB and an average noise figure (NF) of 1.3 dB from 27 to 40 GHz, with a dc power consumption of 0.311 W. The MMIC was also subject to large signal testing, exhibiting an output power at 1-dB gain compression of 9.9 dBm at 35 GHz and surviving an overdrive continuous wave signal at 26 GHz with a power of up to +25 dBm with no significant S-parameter performance degradation. To the best of our knowledge, this is the first demonstration of a Ka-band MMIC LNA in GaN with average NF 1.3 dB from 27 to 40 GHz.