Objective: This study aimed to quantify the interplay between socioeconomic and ethnic inequalities in preterm birth rates using routinely collected maternity data in England from 2018-2021. Design: A retrospective cohort study using electronic health data. Setting: English hospitals. Sample: 1,537,595 livebirths. All women aged 13-55 with a singleton livebirth (April 2018-March 2021) at 24-42 weeks were included. Methods: Multivariate Poisson regression was used to estimate rate of preterm birth in each ethnic and deprivation group. A post-hoc calculation identified the rate of preterm birth for each ethnic group at each level of deprivation. Main Outcome Measures: Preterm birth (livebirth less than 37 weeks). Results: The rate of preterm birth was 6·30% (95%CI:6·22-6·37) in women living in the most deprived areas, compared to a rate of 5·05% (95%CI:4·96-5·14) among women in the least deprived areas. White women had a preterm birth rate of 5·74% (95%CI:5·70-5·78). Whereas South Asian and Black women had higher rates of preterm birth at 6·09% (95%CI:5·98-6·21) and 5·89% (95%CI:5·70-6·09) respectively. Deprivation attenuated the rate of preterm birth across all ethnicity groups. In areas of high deprivation, preterm birth rates were similar across ethnicity groups. In the least deprived areas, South Asian and Black women had higher rates of preterm birth. Conclusion: Deprivation and ethnicity remain key drivers of inequalities in preterm birth. Prevention strategies need to address socioenvironmental and structural determinants of preterm birth in areas of high deprivation and minority ethnicity groups.