R package SiMRiv. Provides functions to generate and analyze individual-based spatially-explicit simulations of multi-state movements in heterogeneous landscapes, based on ”resistance” rasters. Although originally conceived and designed to fill the gap of softwares simulating spatially-explicit trajectories of species constrained to linear, dendritic habitats (e.g., river networks), the simulation algorithm is built to be highly flexible and can be applied to any (aquatic, semi-aquatic or terrestrial) organism. Thus, the user will be able to use the package to simulate movements either in homogeneous landscapes, heterogeneous landscapes (e.g. semi-aquatic animal in a riverscape), or even in highly contrasted landscapes (e.g. fish in a river network). The algorithm and its input parameters are the same for all cases, so that results are comparable. Simulated trajectories can then be used as null models to test e.g. for species site fidelity and other movement ecology hypotheses, or to build predictive, mechanistic movement models, among other things. The package should thus be relevant to explore a broad spectrum of ecological phenomena, such as those at the interface of animal behaviour, landscape, spatial and movement ecology, disease and invasive species spread, and population dynamics. This is the first released experimental version; do test before using in production.