This article surveys the expansion of Russian peasant settlement from 1550, when most of the 6·5 million peasants lived in the forest-heartland of Muscovy, to 1897, when around fifty million Russian peasants lived throughout large parts of the immense Russian empire. It seeks to explain how this massive expansion was achieved with reference to different facets of the ‘frontier’: the political frontier of the Russian state; the environmental frontier between forest and steppe; the lifeway frontier between settled peasant agriculture and pastoral nomadism; and the ‘hierarchical frontier’ between the Russian authorities and the mass of the peasantry. The article draws attention to the different ways in which peasant-migrants adapted to the variety of new environments they encountered, and stresses interaction across each facet of the frontier. Nevertheless, by 1897, the coincidence between the two main types of environment and the two principal lifeways of the population had been virtually eliminated in much of the Russian empire outside central Asia. This was a consequence of the expansion of Russia's political frontiers, mass peasant migration, the ploughing up of vast areas of pasture land, and the sedentarization of many nomadic peoples. The expansion of peasant settlement helps explain the durability of Russian peasant society throughout the period from the mid-sixteenth to the late-nineteenth centuries.