Formal language: This paper discusses inclusive research and epistemic justice by using an example of a published study the authors conducted on intellectual disability and sexuality in supported living environments. Our study addressed taboos and pushed boundaries in content and methodology through two ways of inclusive research: (1) the second author of this paper who has an intellectual disability was a main researcher in the study; and (2) we interviewed people with intellectual disabilities about their own experiences as well as their desired solutions to obstacles they face in their supported living environments. Their input was centralized in the final research report. This method challenged the epistemic injustice of who have historically not been ‘allowed’ to produce knowledge in research. This paper offers historical insight into epistemic injustice as well as relational approaches from critical disability studies and non-Western understandings of disability that ‘rethink’ disability and that can thus promote epistemic justice in academic theory. By addressing both practice and theory in this paper, we aim to contribute to the growing body of inclusive research and to the epistemic justice of people with intellectual disabilities. Plain language: (1) Epistemology = thinking about knowledge, producing knowledge, sharing knowledge. (2) In history, people with intellectual disabilities have often been excluded from participating in this. This is called epistemic injustice. It is caused by the discrimination of people with intellectual disabilities (ableism). (3) Performing inclusive research with people with intellectual disabilities challenges this. It contributes to epistemic justice. Researchers and interviewees with intellectual disabilities can bring knowledge from lived experience into research. (4) Knowledge from lived experience has not always been valued in traditional research. That means we also need to think differently about ‘knowledge’, and about ‘disability’ and its ‘value’. (5) Discrimination based on disability has a long history. For instance: during colonialism by European countries (starting in the 15th century), false ideas about ‘poor health’ and ‘low intelligence’ were already used to justify slavery. People with disabilities have often been locked away or even killed because they have been seen as ‘less valuable’. These ways of thinking still exist. They influence our understanding of ‘epistemology’ because they decide whose way of thinking and way of life is valuable or not valuable. We need to change this way of thinking. (6) Some academic fields that help are critical disability studies, indigenous studies, and feminist posthumanism. These fields challenge ableist ways of thinking. They can help us understand disability as something that is not negative or less valuable, but simply part of what makes us human.