Delivering milliwatts of wireless power at centimeter distances is advantageous to many existing and emerging biomedical applications. It is highly desirable to fully integrate the receiver on a single chip in standard CMOS with no additional post-processing steps or external components. This paper presents a 2 × 2.18 mm ² on-chip wireless power transfer (WPT) receiver (Rx) coil fabricated in 0.13 μm CMOS. The WPT system utilizes a 14.5 × 14.5 mm ² transmitter (Tx) coil that is fabricated on a standard FR4 substrate. The on-chip power harvester demonstrates a peak WPT efficiency of -18.47 dB, -20.96 dB and -20.15 dB at 10 mm of separation through air, bovine muscle and 0.2 molar NaCl, respectively. The achieved efficiency enables the delivery of milliwatts of power to application circuits while staying below safe power density and electromagnetic (EM) exposure limits.