Measuring fast-changing currents in SiC/GaN power electronics is challenging: current changes of hundreds of amperes within nanoseconds demand sensors with high bandwidth, low parasitic inductance, and a compact footprint — requirements conventional shunts, Rogowski coils, and Hall sensors fail to meet simultaneously. The M-Shunt addresses this using a coaxial shunt resistor concept, where the measurement path runs through the centre of a cylindrical conductor. By Ampere's law, this shields the measurement from external magnetic fields, capturing only the true voltage drop free of switching-loop interference. Developed at the University of Bremen, the design integrates this principle into a compact, surface-mountable PCB structure that adds negligible parasitic inductance when embedded in power modules or test setups. Combining high bandwidth, low insertion inductance, high current capability, and EMI stability, the M-Shunt enables applications such as Double Pulse Testing, in-module current sensing, and detecting current asymmetries in the Kelvin Source path of multi-chip modules — tasks unattainable with existing sensors at comparable bandwidth and footprint.