Intricate ecosystem of the human gut microbiome is affected by various environmental factors, genetic makeup of the individual, and diet. Specifically, resistant starch (RS) is indigestible in the small intestine but nourishes the gut microbiota in the colon. Degradation of RS in the gut begins with primary degraders, such as Bifidobacterium adolescentis and Ruminococcus bromii. Recently, new RS degraders, such as Ruminococcoides bili, have been reported. These microorganisms play crucial roles in the transformation of RS into short-chain fatty acids (SCFAs), such as acetate, propionate, and butyrate. SCFAs are necessary to maintain optimal intestinal health, regulate inflammation, and protect against various illnesses. This review discusses the effects of RS on gut and highlights its complex interactions with gut flora, especially the Ruminococcaceae family.