16S rRNA methyltransferases (16S RMTases) confer high-level aminoglycoside resistance (MICs >256 mg/L) to Gram-negative bacteria and are an emerging threat. The prevalence of 16S RMTases in the UK is entirely unknown as are the drivers behind their emergence. The occurrence of 16S RMTases (ArmA, RmtA-RmtH and NpmA) in the UK was identified by screening bacteria from Public Health England’s Antimicrobial Resistance and Healthcare Associated Infections Reference Unit from 2003-2015 and whole-genome sequences from the British Society for Antimicrobial Chemotherapy Resistance Surveillance Project from 2001-2013, with positivity rates of 83.2% (1,312/1,576) and 0.3% (4/1,566), respectively. A prospective surveillance study, where 14 NHS Trusts sent amikacin-resistant bacterial isolates from May 1st to October 31st 2016, determined a period prevalence of 16S RMTases of 0.1% (79/71,063). Potential risk factors for acquisition of 16S RMTase-producing bacteria, were identified using anonymised case questionnaires and included age (≥65 years), being male, an inpatient or a non-UK resident and receiving medical treatment abroad. 16S RMTases were frequently associated with carbapenemases, which were identified in 94.3% (1,237/1,312), 87.3% (69/79) and 50.0% (2/4) 16S RMTase-producing isolates in these isolate collections. 16S RMTases were frequently carried by ‘high-risk’ bacterial clones such as Klebsiella pneumoniae ST14. Analysis of genome sequence data identified mobile genetic elements such as Tn1548 (armA), Tn2 (rmtB), ISEcp1 (rmtC) and IS91 (rmtC and rmtF) were associated with 16S RMTases. Analysis of plasmids identified genetic linkage of 16S RMTases with the carbapenemase NDM-1 and the circulation of novel plasmids within the UK. Although currently rare in the UK, 16S RMTases appear to be emerging through clonal expansion, and potentially through association with carbapenemases and mobile genetic elements. Given the critical therapeutic role of aminoglycosides in combatting the challenge of antimicrobial resistance in Gram negative pathogens, the risk of future emergence is high, underlining a need for ongoing surveillance.