In this paper we present the design and measurement results, both on-wafer and in package, of an ultra-low-noise and wideband monolithic microwave integrated circuit (MMIC) amplifier in the frequency range of 75 to 116 GHz. The three-stage amplifier packaged in a WR10 waveguide housing and fabricated using a 35-nm InP HEMT technology achieves a record noise temperature of 23 K at 108 GHz when cryogenically cooled to 27 K. The measured gain is 22 to 27 dB for frequency range of 75 to 116 GHz. Furthermore, the amplifier utilizes four-finger devices with a total gate width of 60 μm resulting in higher output power. Therefore, we consider that this amplifier achieves state-of-the-art performance in terms of bandwidth, noise temperature, gain, and linearity so far reported for cryogenically cooled amplifiers around W-band.