Our project is called RESIDE (RElationships and Sexuality in Intellectual Disability Education) because it refers to a power or right belonging to a person. We believe that it is every Children and Young Person's (CYP) right to be provided with evidence-based, effective Relationships and Sexuality Education (RSE) so that they can make informed, safe choices about their relationships. Approximately 2.5% of the UK population have an intellectual disability (ID), equating to 1.5 million people, of which there are 286,000 children-180,000 boys, 106,000 girls aged 0-17 years. Young people with intellectual disabilities want friendships and relationships yet may have few beyond immediate family members, leading to an absence of social networks and increased isolation. Some may want intimate relationships that can involve sex, and some are sexually active. While for some, their relationships can be rewarding and fulfilling, others may experience harm and exploitation, sexually transmitted infections and unintended pregnancies. In response, parents can seek to protect their family member from harm, further limiting life opportunities. Findings from our systematic review showed that no evidence based, rigorously evaluated RSE programmes for CYP with ID currently exist. While many schools create programmes, or use materials taken from online sources, these may not always be appropriate for pupils with ID. Many such programmes fail to take a life course approach to providing education about RSE which extends beyond their time at school. Our UK wide qualitative study showed that CYP wanted information on friendships, sex, contraceptive use, and abusive relationships while parents were concerned about safety (in-person and online), respecting boundaries and consent. Both CYP and parents wanted to learn about relationships and mental health. This project will build on established relationships with our project advisory group to co-produce an evidence-based intervention, informed by our previous work, to deliver RSE to CYP with ID. We will update our systematic review published in 2020, combine this with findings from our qualitative study and utilise a model of knowledge translation to create materials for inclusion in a RSE programme. We will create a bespoke website to host these materials and will test their acceptability with CYP with ID (n=90-120) and parents (n=90-120) via questionnaire across England, Scotland and Norther Ireland. We will also recruit CYP with ID (n=12), parents (n=12) and educators (n=12), to take part in semi-structured interviews to explore acceptability in greater detail. This information will be used to further refine the programme. In future phases of the project, we will seek to test the feasibility and effectiveness of the programme in increasing CYP with ID's knowledge and understanding of RSE, reducing unintended pregnancies and reducing sexually transmitted infections.