Due to the fact that phenomena such as globalization, integration, migration, and progress in information and communication technology have all contributed to making the world a much more complex place than it used to be, there are strong reasons for considering complexity as a key aspect of various topics of interest for the social sciences. The overall objective of this PhD dissertation is to explore the possibility of approaching language policy and planning (LPP) from the perspective of complexity theory. In a first step, I provide a definition of complexity and put it an LPP perspective. I introduce the notion of “complexity”, trying to spell out its basic characteristics. I plan to discuss how and why it is receiving increasing attention in the social sciences. In a second step, I look at selected LPP issues and reinterpret them under the lens of complexity theory by applying its tools and methods.