Abstract Gastric cancer (GC) is one of the most common malignancies globally, the occurrence of which undergoes a multistage chronic evolutionary process. It is a great public health issue to deeply understand the mechanisms of GC development and factors affecting the evolution of gastric lesions. Helicobacter pylori infection has been identified as one of the main factors for gastric carcinogenesis and microbial dysbiosis. With the advances in molecular biology techniques, other gastric microbes besides H. pylori have been observed to play an essential role in the development of GC. Previous animal model studies suggested that specific and critical microbes in the stomach can accelerate the malignant transformation of gastric mucosa and the progression of gastric lesions to GC. Recently, the composition of human gastric microbiota has been investigated from stages of precancerous lesions to GC, including characteristics of gastric microbiota diversity, lesion‐associated differential microbes, predicted microbiota‐related functions, microbiota interactions, and microbial mechanisms in gastric carcinogenesis. In this review, we provide an overview of the gastric microbiota, summarize current studies exploring the roles of microbiota in gastric carcinogenesis, and illustrate the significance and prospects of integrative multiomics analysis combined with the microbiome in gastric carcinogenesis.