This article presents the design and characterization of a direct current (dc) sensor utilizing the Hall effect in AlGaN/GaN 2-D electron gas (2DEG) four-terminal devices and a flux concentrator. The sensor was fabricated from an AlGaN/GaN/Si wafer grown by metal-organic chemical vapor deposition. The sensor exhibited excellent linearity and repeatability with a high Hall voltage under the primary current ranging from -5 to 5 A. The sensitivity of the sensor was measured to be 0.26 (V/A)/A at 20 °C and independent of ambient temperature up to 200 °C. The obtained result is greater than that of other reported Hall effect-based current sensors. The high sensitivity and thermal stability at varying temperatures are attributed to the high electron mobility, wide bandgap, and stability of carrier density in 2DEG. Combining these factors with the excellent mechanical strength, electrical conductivity, and chemical inertness of GaN, the proposed sensor is promising for current monitoring in a wide range of operation temperatures.