The quality of romantic relationships is associated with mental health and wellbeing throughout the life course. A number of programmes have been developed to support young people in navigating healthy relationships, and a larger role for relationship education was recently formalised in statutory guidance in England. This study aimed to systematically review the evidence base for relationship education programmes. Evaluations of relationship education programmes for young people, including charting of outcome domains and measures, were reviewed, followed by a focussed synthesis of data from studies that included outcome domains of relevance to healthy relationships. Thirty-six studies of seven programmes were found that focussed on one or more outcomes relating to healthy relationship skills, knowledge and attitudes, none of which were assessed as high quality. All evaluated programmes were developed in the US, and only one evaluation was conducted in the UK. The evaluations had a diverse set of outcome domains and outcome measures, few had longitudinal measures. No evidence was found for young people's involvement in programme or evaluation development. High-quality longitudinal evaluations and a core set of validated outcome measures are needed. This research also highlights the need to co-create programmes with young people, teachers and relationship experts that are feasible, acceptable and integrated into a mental health-informed curriculum.