Sexual offending is an emotive and complex issue that psychologists and allied professionals have studied extensively. The impact of sexual offending on victims/survivors is profound and, in many cases, life-changing. The level of media and public interest in sexual offending continues to increase and whilst this interest has undoubted benefits, including victims/survivors having the confidence to report sexual crimes, misunderstanding regarding those who sexually offend is commonplace. This is why developing an in-depth and critical understanding of theories that seek to explain sexual offending and societal factors which have influenced theory development is essential for those studying forensic psychology. Convictions for sexual offences increased by 40% from 2019 to 2023 within the United Kingdom, with convictions for rape increasing by 58% from 2019 to 2023 (Ministry of Justice, Accredited official statistics: Criminal justice statistics quarterly for December 2023, https://www.gov.uk/government/statistics/criminal-justice-system-statistics-quarterly-december-2023 , 2024). This means it is possible that those choosing a career in forensic psychology, whether it be in academia or in applied practice, will at some point need to explore sexual offending. This chapter will provide a critical timeline of the societal and cultural contexts in which sexual offending and sexually harmful behaviour have been understood in recent centuries. This chapter will go on to describe the evolution of specific types of sexual offending theory, highlighting the role of forensic psychology within the theory development and implications for psychological practice. This chapter will finish by discussing a current integrated psychological theory of sexual offending and how the theory translates into applied psychological practice when working with those who have sexually offended.