In this paper, the gate current in AlGaN/GaN high-electron mobility transistors is modeled analytically in a surface potential-based compact model. Thermionic emission and Poole-Frenkel emission are two dominant mechanisms for the gate current in the forward and reverse-bias regions, respectively. In addition, a trap-assisted tunneling component, which is important at low reverse bias, is also added. The developed gate current model, implemented in Verilog-A is in excellent agreement with experimental data and passes the important Gummel symmetry test.