Two-dimensional (2D) indium arsenide (InAs) is promising for future electronic and optoelectronic applications such as high-performance nanoscale transistors, flexible and wearable devices, and high-sensitivity broadband photodetectors, and is advantageous for its heterogeneous integration with Si-based electronics. However, the synthesis of 2D InAs single crystals is challenging because of the nonlayered structure. Here we report the van der Waals epitaxy of 2D InAs single crystals, with their thickness down to 4.8 nm, and their lateral sizes up to ~ 37 μm. The as-grown InAs flakes have high crystalline quality and are homogenous. The thickness can be tuned by growth time and temperature. Moreover, we explore the thickness-dependent optical properties of InAs flakes. Transports measurement reveals that 2D InAs possesses high conductivity and high carrier mobility. Our work introduces InAs to 2D materials family and paves the way for applying 2D InAs in high-performance electronics and optoelectronics.