Abstract: The control of electromagnetic waves lies at the core of many modern technologies. Naturally occurring materials provide only limited electromagnetic response, particularly in the challenging terahertz (THz) frequency range, which is insufficient for emerging technologies with increasingly demanding requirements. Metamaterials are a class of effective media that allow for exotic electromagnetic properties by tailoring their composite metallic/dielectric subwavelength structures. Metasurfaces, the two-dimensional equivalent of metamaterials, can provide desirable functionalities suitable for device applications and, at the same time, address the loss and fabrication issues. In this talk I will present our recent advances in metasurfaces for manipulating the amplitude, phase, polarization, and propagation of THz waves. These include antireflection, polarization conversion, beam focusing, and signal modulation. The metasurface approach shows significant advantages in performance and device simplicity, as compared to conventional THz devices and components, and can be also scaled to operate at other wavelength ranges.