Background: Kratom (Mitragyna speciosa Korth) use has increased in Western countries, with a rising number of associated deaths. There is growing debate about the involvement of kratom in these events. Aims: This study details the characteristics of such fatalities and provides a ‘state-of-the-art’ review. Methods: UK cases were identified from mortality registers by searching with the terms ‘kratom’, ‘mitragynine’, etc. Databases and online media were searched using these terms and ‘death’, ‘fatal*’, ‘overdose’, ‘poisoning’, etc. to identify additional cases; details were obtained from relevant officials. Case characteristics were extracted into an Excel spreadsheet, and analysed employing descriptive statistics and thematic analysis. Results: Typical case characteristics (n = 156): male (80%), mean age 32.3 years, White (100%), drug abuse history (95%); reasons for use included self-medication, recreation, relaxation, bodybuilding, and avoiding positive drug tests. Mitragynine alone was identified/implicated in 23% of cases. Poly substance use was common (87%), typically controlled/recreational drugs, therapeutic drugs, and alcohol. Death cause(s) included toxic effects of kratom ± other substances; underlying health issues. Conclusions: These findings add substantially to the knowledge base on kratom-associated deaths; these need systematic, accurate recording. Kratom’s safety profile remains only partially understood; toxic and fatal levels require quantification.