Insomnia is a common yet challenging symptom to manage in primary care due to its broad differential diagnoses and underlying complexity. As a prevalent sleep disorder, it significantly reduces quality of life, making it a key concern in primary care practice. This chapter explores the background of insomnia, examining its potential causes and risk factors—ranging from psychological and lifestyle contributors to underlying medical conditions—and its overall impact on health. It aims to provide clinicians with practical tools for the effective assessment and diagnosis of insomnia. Management strategies are summarized, with a focus on evidence-based interventions such as cognitive behavioural therapy for insomnia (CBT-I), pharmacological options (including commonly used medications and dosages), and lifestyle modifications.