This paper presents a K-band CMOS low-noise amplifier (LNA) incorporating a Q-enhanced notch filter. The third-order notch filter composed of two capacitors and one high-Q inductor is used for low-side interference-rejection (IR). Moreover, the proposed inductor is realized by a tapped-inductor feedback topology to compensate its resistive losses with low-power consumption. The LNA is designed and implemented successfully in a standard 0.18-µm CMOS process. The circuit consumes 10.7mW with a chip size of 0.6mm². Measured results demonstrate 10.5-dB gain, 4.7-dB NF, 16-dB input return loss, 13.5-dB output return loss, -10.5-dBm input P_1dB, and -3.6-dBm IIP3 at 23GHz, respectively. The circuit also shows a 33.5-dB rejection level at 17.9GHz.