Thermokarst refers to landforms and processes resulting from the thaw of ice-rich permafrost. Thermokarst landforms vary with ground ice, substrate, and terrain conditions, which are products of geological and climatic history. Recognizing how thermokarst manifests across vast permafrost regions provides insights into the consequences of permafrost thaw, including sediment fluxes, carbon cycling, and ecosystem changes. Here, we present a conceptual model summarizing associations between thermokarst landforms and permafrost terrain conditions, based on a compilation and analysis of 19,549 landform observations from published literature. We recognize several broad thermokarst domains in Canada, based on permafrost and ground ice distribution and past climate, further modified by organic terrain conditions, which control landform types and their general distribution. These domains broadly group the distribution of thermokarst landforms observed today and suggest the range of thermokarst trajectories expected with future climate warming. The conceptual model supports the narrative expressed in the production of the Ground Ice Map of Canada and the permafrost landsystems framework, i.e., that geological and paleoenvironmental histories, including impacts of past thaw, influence the nature and variation in ground ice and thermokarst across permafrost regions.