These lectures cover some of the basics of modern cosmology, assuming relatively little prior knowledge of the subject. They are organised into three main sections: (1) Models of the expanding universe (the Robertson-Walker metric, dynamics and the equation of state, the hot big bang, initial conditions and inflation); (2) Dark matter (astrophysical mass measurements, particle candidates for dark matter, constraints on dark matter from galaxy haloes, dark matter and cosmological perturbations); (3) Structure formation (statistics of cosmological density fields, generation of fluctuations via inflation, observations of large-scale structure, fluctuations in the microwave background).