is a common sexually transmitted infection. Treatment guidelines focus on those with symptoms and sexual contacts, generally with regimens including doxycycline and/or azithromycin as first-line and moxifloxacin as second-line treatment. We investigated the prevalence of antimicrobial resistance (AMR)-conferring mutations in among the sexually-active British general population.The third national survey of sexual attitudes and lifestyles (Natsal-3) is a probability sample survey of 15 162 men and women aged 16-74 years in Britain conducted during 2010-12. Urine test results for were available for 4507 participants aged 16-44 years reporting 1 lifetime sexual partner. In this study, we sequenced regions of the 23S rRNA and genes to detect known genotypic determinants for resistance to macrolides and fluoroquinolones respectively.94% (66/70) of specimens were re-confirmed as positive, with successful sequencing in 85% (56/66) for 23S rRNA and 92% (61/66) for genes. Mutations in 23S rRNA gene (position A2058/A2059) were detected in 16.1% (95%CI: 8.6% to 27.8%) and in (encoding D87N/D87Y) in 3.3% (0.9%-11.2%). Macrolide resistance was more likely in participants reporting STI diagnoses (past 5 years) (44.4% (18.9%-73.3%) vs 10.6% (4.6%-22.6%); p=0.029) or sexual health clinic attendance (past year) (43.8% (23.1%-66.8%) vs 5.0% (1.4%-16.5%); p=0.001). All 11 participants with AMR-conferring mutations had attended sexual health clinics (past 5 years), but none reported recent symptoms.This study highlights challenges in management and control. Macrolide resistance was present in one in six specimens from the general population in 2010-2012, but no participants with AMR reported symptoms. Given anticipated increases in diagnostic testing, new strategies including novel antimicrobials, AMR-guided therapy, and surveillance of AMR and treatment failure are recommended.