Internalised stigma is highly prevalent among people with mental illness. This is concerning because internalised stigma is often associated with negative consequences affecting individuals' personal, familial, social, and overall wellbeing, employment opportunities and recovery. Currently, there is no psychometrically validated instrument to measure internalised stigma among Xhosa people in their home language. Our study aimed to translate the Internalised Stigma of Mental Illness (ISMI) scale into isiXhosa. Following WHO guidelines, the ISMI scale was translated using a five-stage translation design which included (i) forward-translation, (ii) back-translation, (iii) committee approach, (iv) quantitative piloting, and (v) qualitative piloting using cognitive interviews. The ISMI isiXhosa version (ISMI-X) underwent psychometric testing to establish utility, within-scale validity, convergent, divergent, and content validity (assessed using frequency of endorsements and cognitive interviewing) with