Light can be considered a clean, renewable, and inexpensive “reagent” for chemical synthesis. Nevertheless, most conventional methods for the photochemical synthesis of organic compounds require the use of specialized photochemical equipment that is capable of generating high-energy ultraviolet light and containing it safely. This is a practical impediment that has prevented the wide adoption of photochemical synthesis in the fine chemicals industry. We have developed a strategy that exploits the reactivity of transition metal photocatalysts in order to perform a variety of synthetically useful cycloaddition reactions using visible wavelengths of light. By enabling the use of direct sunlight rather than high-energy artificial UV light, we hope to establish a new, environmentally responsible approach to synthetic organic photochemistry.