We present the first fully CMOS-integrated 3D Hall probe. The microsystem is developed for precise magnetic field measurements in the range from mT up to tens of tesla in the frequency range from DC to 30 kHz and with a spatial resolution of about 150 μm. The microsystem is realized in a conventional CMOS process without any additional processing step and can be manufactured at very low cost. With the electronics circuit applying the so-called spinning-current technique to the Hall sensor block, we obtain low noise (a resolution better than 100 μT) and low cross talk between the channels (less than 0.2% between the channels up to 2 T). The single chip configuration insures a precision of the orthogonality between the measurement axes better than 0.5°. A temperature sensor based on a band-gap cell is integrated directly on the chip, which allows a good temperature drift compensation of the system.