Helicobacter pylori is a bacterium that colonises the human stomach and is the major risk factor for several gastroduodenal diseases, including gastric cancer. Currently, we know that the stomach harbours a complex microbial community, but the impact of the gastric microbiota in the promotion of health or disease is not fully understood. The present article is a review of the most relevant literature published between April 2019 and March 2020 exploring the role of the microbiota in gastric diseases. During this period, the great majority of the publications focused on the modulation of the gastric microbiota by Helicobacter pylori infection, and on the relationships between the gastric and gut microbiotas and gastric tumorigenesis.