We present the first demonstration of a Yb:CALGO thin-disk laser. In a slightly multimode configuration, we obtained up to $30\mathrm{W}$ of average power at a slope efficiency of 40% and an optical-to-optical efficiency of 32%. With a single-mode cavity, an average power of $25\mathrm{W}$ was achieved. A tuning range from 1018 to $1052\mathrm{nm}$ could be demonstrated by inserting a prism into the cavity. In the Q-switched regime, we obtained $1\mathrm{mJ}$ of pulse energy at a repetition rate of $100\mathrm{Hz}$ .