In this lecture, Dr. Lianne Lefsrud (University of Alberta) discusses effective risk communication, and how it is fundamental to addressing sustainability challenges such as developing climate change policies, enhancing workplace safety, and promoting public health. This lecture begins with an overview of risk definitions, how risk is assessed, and how risk acceptability is evaluated. Then, we will outline when and with whom you would communicate risks and the associated barriers to risk communication. We will conclude with overarching principles for effective communication: determining key audiences, defining the purpose of a risk communiqué, using the most effective method of communicating (visual, verbal, statistics, combinations), and using the most credible messenger. Ample examples will be given throughout.