Electric toothbrushes are the most effective method for maintaining oral hygiene, but also the method with the greatest environmental impact. Most of the impact of electric toothbrushes comes from transport, materials and parts. This means that by extending the product life and enabling local loops, the environmental impact of electric toothbrushes can be reduced. The circular economy encompasses multiple strategies that can be leveraged to achieve this. So far, there has been little research into designing small waterproof personal care appliances for the circular economy. In this thesis, the challenges and opportunities for transitioning electric toothbrushes to the circular economy are uncovered and a design solution to these challenges and opportunities is proposed. The primary research question for this thesis is: How can an electric toothbrush be designed suitable for the circular economy? The first two phases of this thesis were dedicated to uncovering the challenges and opportunities for transitioning electric toothbrushes to the circular economy. In the first phase, research into the state of the circular economy of current electric toothbrushes was performed in which the academic, manufacturer and user perspectives were researched. This led to three key insights for the circular design of an electric toothbrush. In the second phase, an analysis was performed of the implementation of circular design strategies in a representative set of current electric toothbrushes. This led to four key insights for the circular design of an electric toothbrush. In the third phase of the thesis, the key insights were translated to design challenges and a design solution to tackle these design challenges was conceived. This resulted in the Everbrush electric toothbrush concept. The battery has been made user replaceable to tackle the primary reason for reaching the end of life, reduced battery performance. An aluminium main body was introduced that aims to increase product attachment by ageing with dignity, which should also increase repair considerations. Another aim of the aluminium main body is to reduce hygiene concerns when purchasing refurbished. The ease of disassembly has been improved significantly which can open up additional opportunities for product life extensions. The amount of elastomers has been reduced by introducing a rotating magnetic power switch, eliminating the need for a power switch seal and increasing high-value recycling performance. Lastly, permanent connections were avoided throughout the design, also increasing high-value recycling performance.