We present UniTune, a simple and novel method for general text-driven image editing. UniTune gets as input an arbitrary image and a textual edit description, and carries out the edit while maintaining high semantic and visual fidelity to the input image. UniTune uses text, an intuitive interface for art-direction, and does not require additional inputs, like masks or sketches. At the core of our method is the observation that with the right choice of parameters, we can fine-tune a large text-to-image diffusion model on a single image, encouraging the model to maintain fidelity to the input image while still allowing expressive manipulations. We used Imagen as our text-to-image model, but we expect UniTune to work with other large-scale models as well. We test our method in a range of different use cases, and demonstrate its wide applicability.