This talk will discuss recent advances in the nascent field of integrated photonic circuits for terahertz applications. This field explores photonic circuit technology to create miniaturized terahertz emitters and detectors by non-linear optical processes that cannot be realized with other technologies. It leverages the unprecedented design flexibility offered by chipscale components such as waveguides, resonators and terahertz antennas in combination with low-loss and high-performance nonlinear materials. The talk will concentrate on two of the recently emerging material platforms - thin film lithium niobate and hybrid organics-on-SOI - and elaborate on the fundamental working principles of both high-sensitivity detectors and customtailored emitters. Their present and future applications in fundamental research concerning metrology, photon generation and arbitrary waveform synthesis will be discussed.