[en] Electron Cyclotron Heating and Current Drive (ECH(and)CD) systems are a major part of nuclear fusion technology as localised and steerable deposition of high power mm-waves contributes essentially to plasma start-up, plasma heating, shaping of current profiles, and plasma stabilisation. At ITER, the first tritium confinement in the mm-wave launchers will be formed by CVD diamond windows. Based on large area CVD diamond disks and their unparalleled combination of ultralow mm-wave absorption and outstanding thermal conductivity, the window design for front steering (FS) and remote steering (RS) launchers was worked out for a transmission capability of 2 MW at the fixed frequency of 170 GHz. In addition, a torus window was designed for a step-tuneable Electron Cyclotron wave system for ASDEX Upgrade for transmission of up to 1 MW mm-wave power at 4 selected frequencies between 105 - 140 GHz. The designs for the torus windows for the three different launcher concepts account for the specific transmission requirements. For single-frequency operation, a single disk configuration was established. The disk thickness is adapted to provide sufficient safety margin towards pressure rise in the vacuum vessel (0.2 MPa) for the required window aperture. For the RS launcher, the remote steering unit placed in the back-end of the launcher requires a large window aperture (95 mm) to avoid beam vignetting at the extreme steering angles of ±12 ^o. For the FS launcher with the steering mechanism placed in the front shield of the launcher, the disk size is reduced as the window aperture can be identical to the waveguide inner diameter (63.5 mm). This allows to consider indirect cooling instead of edge cooling and thus to eliminate the risk of tritium contact to the cooling water in case of crack formation in the diamond disk. For the multi-frequency torus window at ASDEX-Upgrade a double disk configuration with the disk separation of 5 mm, fine tuneable over ± 1 mm, is realised. The paper discusses the design guidelines and the thermohydraulic and thermo-mechanical analysis of the three window concepts. The prototypes of the high power windows were manufactured. Details of the thermohydraulic and of the mm-wave performance tests are discussed. For the single disk windows, the tool development is presented which provides on-site replacement of the ITER torus window by automated cutting and welding tools. (author)