A radiotherapy apparatus includes a fixed support and a gantry including a chassis part and a source part, the chassis part being rotatably attached to the fixed support to allow rotation thereof about a generally horizontal axis, and the source part being connected to the chassis part via a rotatable connection allowing the source part to rotate relative to the chassis part around a transverse axis. The source part includes a source of therapeutic radiation directed towards the intersection of the transverse axis and the horizontal axis. The chassis part and the source part together define an annular ring that encircles the horizontal axis. In this way, the radiotherapy apparatus can provide the full usual range of treatments, but can also adapt itself to adopt a non-coplanar geometry when required, for example to treat difficult locations in the head and neck.