Due to the emergence of electric vehicles, power electronics have become the new focal point of research. Compared to commercialized semiconductors, such as Si, GaN, and SiC, power devices based on β-Ga2O3 are capable of handling high voltages in smaller dimensions and with higher efficiencies, because of the ultrawide bandgap (4.9 eV) and large breakdown electric field (8 MV cm-1). Furthermore, the β-Ga2O3 bulk crystals can be synthesized by the relatively low-cost melt growth methods, making the single-crystal substrates and epitaxial layers readily accessible for fabricating high-performance power devices. In this article, we first provide a comprehensive review on the material properties, crystal growth, and deposition methods of β-Ga2O3, and then focus on the state-of-the-art depletion mode, enhancement mode, and nanomembrane field-effect transistors (FETs) based on β-Ga2O3 for high-power switching and high-frequency amplification applications. In the meantime, device-level approaches to cope with the two main issues of β-Ga2O3, namely, the lack of p-type doping and the relatively low thermal conductivity, will be discussed and compared.