Purpose: Recent data argue for the involvement of inflammatory and infectious diseases in cancer development. However, clinical data on the association between chronic gingivitis and cancer have been less conclusive. Here, we systematically evaluated the cancer incidence in a population-based cohort of outpatients with chronic gingivitis from the United Kingdom. Methods: 9891 patients with chronic gingivitis and an identical number of people without gingivitis matched by age, gender, index year, and the Charlson Comorbidity Index were identified from the Disease Analyzer database (IQVIA) between January 2000 and December 2016. Cox regression models were used to study the association between gingivitis and cancer. Results: The probability of cancer was significantly higher among patients with diagnosed chronic gingivitis compared to non-gingivitis individuals (HR = 1.36, 95% CI = 1.15–1.62). In cancer site-stratified analyses, we observed a trend towards higher rates of cancer in almost all cancers (breast cancer, lymphoid system cancer, digestive tract cancers, skin cancer); however, a significant association was only observed for prostate cancer (HR: 3.38; 95% CI: 1.57–7.27). Notably, the largest increase in cancer rates was observed in male patients (HR: 1.46, 95% CI: 1.13–1.89) between 41 and 60 years old (HR: 1.74, 95% CI: 1.30–2.32). Conclusions: Our data suggest that chronic gingivitis represents an important risk factor for the development of cancer. Therefore, in the context of patient dental care, awareness should be raised to refer gingivitis patients to existing screening programs, especially for prostate cancer. Moreover, the consistent treatment of gingivitis could potentially have a positive impact on the morbidity of certain cancers.