Aims: Permanent treatment of morbid obesity with medication or diet is nearly impossible. Laparoscopic sleeve gastrectomy (LSG) is becoming a widely accepted treatment option. This study profiled and compared gut microbiota composition before and after LSG. Methods & results: A total of 54 stool samples were collected from 27 morbidly obese individuals before and after LSG. The gut microbiota was profiled with 16S amplicon sequencing. After LSG, patientsdemonstrated asignificant decrease (p<0.001) in BMI and an increase in bacterial diversity. An increased Firmicutes/Bacteroidetes ratio was also noticed after LSG. The families Prevotellaceae and Veillonellaceae predominated in preoperative samples but were markedly lowered after LSG. A marked increase in Akkermansia, Alistipes, Streptococcus, Ruminococcus and Parabacteroides was observed after LSG. Conclusion: In addition to lowering BMI, LSG remodeled gut microbiota composition.