Introduction: One in nine women experience endometriosis, a common gynaecological disease, yet time to diagnosis averages 7 years. People are sharing their endometriosis experiences online. This research’s aim was to expose and synthesise the collective themes of diagnostic experience. Method: A qualitative thematic analysis of publicly accessible online autobiographical accounts of women and their endometriosis diagnosis. Themes were coded within NVIVO and thematic maps and tables created. Eighty-nine original accounts were identified, 26 were excluded. Saturation point was 49. Results: Women communicated long, painful and emotional journeys to diagnosis. Forty women experienced endometriosis symptoms before the age of 20, 33 before 15 years. Despite repeated GP presentation, 36 women had never heard of endometriosis before diagnosis. Women highlighted the positive impact of ‘that one doctor’ who said the word ‘endometriosis’ who listened, believed, investigated and provided prompt referral to specialists. Diagnosis gave relief and answers to the long journey, provided women a sense of community, hope and personal visibility after feeling alone. While this common disease is undiagnosed women suffer. Conclusion: ‘That one doctor’ can transform a patient’s experience and create a positive diagnosis pathway towards endometriosis. The doctor patient alliance is vital for prompt diagnosis. Symptom dismissal with long diagnosis delays are having negative, physical and psychological consequences for women. Early detection, GP education and community awareness campaigns are imperative to reduce further delayed diagnosis and long-term negative impacts of undiagnosed endometriosis.