Statement of the Problem: Oral Lichen planus (OLP) is an autoimmune mucocutaneous disease. There are some reports of thyroid diseases, especially hypothyroidism, to have association with OLP in some studies.Purpose: Based on the controversial results of former studies in other populations about the association of hypothyroidism and OLP, the current study aimed to evaluate this association in a sample of Iranian population.Materials and Method: This retrospective comparative study evaluated 523 patients with OLP referring to the Oral and Maxillofacial Department of Shiraz Dental Faculty as the test group and 523 age- and sex-matched patients as the control group. Those participants with oral lichenoid reactions and other mucosal lesions were excluded. The odds ratio (OR) with 95% confidence intervals (CI) for the association of OLP and thyroid diseases were estimated by logistic regression adjusted for the matched age and sex.Results: In the test group, 74% (n=387) and in the control group 73.8% of the patients were female (n=386). In the test group, 26% (n=136) and in the control group 26.2% of the samples were male (n=137). A total of 4% of the patients in the control group (n=21) and 6.7% in the case group (n=35) had a history of hypothyroidism. The reported OR for association of thyroid disease and OLP was 1.714 (CI=0.984-2.987).Conclusion: The results of this study showed no significant association between hypothyroidism and OLP in comparison with the age- and sex-matched control group.Key Words: Hypothyroidism; Oral lichen planus; Association; Hashimoto disease;  Levothyroxine