The discovery of 2D anisotropic semiconductors with high carrier mobility is critical for highly efficient polarization-sensitive devices. Here, we explore the unique properties of an unexpected, yet highly-promising 2D chalcogenide, gold selenide (AuSe) with high stability, ultrahigh and anisotropic carrier mobilities. Linear (AuII) and square-planar (AuIV) channels coexist in 2D AuSe, leading to the remarkable in-plane anisotropy. Electrons favour transport along the a direction with mobility up to 3.98 × 104 cm2 (V s)-1, whereas hole mobility along the b direction (over 8000 cm2 (V s)-1) is almost 40 times larger than that along the a direction. The carrier mobility of 2D AuSe is much higher than most widely-studied 2D semiconductors, such as MoS2 and phosphorene. Moreover, 2D AuSe shows almost full spectral solar absorption, relying on the proper bandgaps. The combination of the separation of ultrafast electron and hole transport channels (AuIV and AuII) and efficient solar absorption enables 2D AuSe great potentials in multifunctional optoelectronics.