A Kerr-lens mode-locked (KLM) Yb:YAG thin-disk oscillator delivering 215-fs pulses with 75-W average power and 1.4-MW peak power at a repetition rate of 260 MHz is presented. Self-starting KLM is demonstrated at an output power of 68 W. This is the highest repetition rate of any mode-locked thin-disk oscillators so far. Concepts for scaling the repetition rate up to 1 GHz are discussed.