The 20th century was defined by growth and consumption as the central drivers of the economy. Entering the 21st century, however, the global tide has begun to shift toward regeneration and circulation. The former industrial model was based on a linear flow of “make, sell, dispose” — the so-called Linear Economy. While this efficiency-driven system generated short-term profits, it also rapidly accelerated negative side effects such as resource depletion, climate change, and the growing waste crisis. In response to these side effects, a new economic philosophy emerged—primarily in Europe—known as the Circular Economy. Its principle is simple yet transformative: keep materials and energy in circulation rather than discard them. Instead of “consuming” resources, we reuse, redesign, and regenerate them. This shift is giving rise to a new relationship between business, society, and design. This article explores the idea of circulation as design—a concept shaping our collective future—through the following three perspectives: 1. The overall framework of the circular economy and sustainability 2. The connection between circular economy and design thinking 3. Practical perspectives on circular design