The bacterium Neisseria gonorrhoeae causes the sexually transmittable infection (STI) gonorrhoea, one of the most prevalent STIs world-wide. Treatment and control of gonorrhoea is threatened by antimicrobial resistance (AMR), since N. gonorrhoeae has developed resistance to all antibiotics formerly used for gonorrhoea treatment. Rare cases of resistance to the currently used antibiotic ceftriaxone have already been detected in multiple countries. Although ceftriaxone resistant N. gonorrhoeae strains are not yet found in the Netherlands, an increase in ceftriaxone reduced susceptible strains was detected. In this PhD thesis, genomics approaches are used to characterise and track AMR mechanisms in N. gonorrhoeae between 2014 and 2020 in Amsterdam. We validated a novel molecular assay to be able to quickly detect fluoroquinolone resistance (chapter 2). With regard to ceftriaxone susceptibility in Amsterdam, we identified that ceftriaxone reduced-susceptibility increased between 2014 and 2019, due to the emergence of multiple ceftriaxone-reduced susceptible strains (chapter 3). After 2019, ceftriaxone reduced-susceptible strains disappeared again and especially during the COVID-19 pandemic, a low-level azithromycin resistant strain emerged, potentially due to more local N. gonorrhoeae transmission during the lockdown (chapter 4). We also used genomics approaches for the surveillance of extended-spectrum cephalosporin-resistant Escherichia coli among men who have sex with men (chapter 5), to identify the N. gonorrhoeae accessory genome and its association with AMR (chapter 6) and to assess within-host genetic variation in N. gonorrhoeae over the course of infection (chapter 7). These last chapters yielded novel insights in the biology of N. gonorrhoeae, which can be used to better understand – and potentially curb – AMR development and spread.