Background: Chronic kidney disease (CKD) is commonly comorbid with hypertension, diabetes and cardiovascular disease (CVD). However, the extent of comorbidity in CKD across a wider range of conditions is not well documented. Aim: To ascertain the prevalence of comorbidity (across 39 physical and mental health comorbidities) in adults aged 25 years and over with CKD in a large nationally representative primary care population. Design and Setting: Cross-sectional analysis of a primary care dataset representing 1,274,374 adults in Scotland. Method: Secondary analysis of general practice electronic medical record data. Comparison was made with the entire population without CKD, standardised for age, sex, and socioeconomic status (SES). Results: A total of 98.2% of adults with CKD had at least one comorbidity (vs. 51.8% in controls). After adjustment for age, sex, and deprivation, people with CKD were more likely to have 1-3 conditions (OR 11.2, 95% CI 10.3-12.2), 4-6 conditions (OR 24.9, 95% CI 22.9-27.0), and ≥7 conditions (OR 38.9, 95% CI 35.6-42.6. Furthermore, all concordant (7 out of 7) and the majority of discordant physical health conditions (17 out of 24) and mental health conditions (6 out of 8) had significantly positive associations with CKD after adjustment. Conclusion: CKD is associated with extreme comorbidity, across a wide range of mental and physical conditions. Routine care for people with CKD should include recognition and management of comorbidities and clinical guidelines should support clinicians to do this.