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, patients demonstrated a significant 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.