Smartphones are one of the groundbreaking technological developments of the last 20 years and their introduction has led to rapid changes in the way we work, socialise, and behave. However, there has been significant concern about potential harms associated with smartphones, including the possibility of smartphone addiction. This introductory chapter is designed to provide context to the importance of understanding smartphone use within our society and its proposed addictive properties. We explore why smartphone addiction has been proposed as a public health matter, how it overlaps with other proposed behavioural addictions, and the ongoing parallel consideration of ‘screen time’. This chapter further contextualises the current political and legislative climate around smartphone use, addiction, and the impact they may have on mental health.