This chapter primarily discusses regional electromagnetic and magnetotelluric studies with a focus on electrical conductivity models of the lithospheric mantle for various tectonic settings. A short review of electromagnetic methods used in lithosphere studies is based largely on Vozoff (1986, 1991), Chave et al. (1991), Hermance (1995), Jones (1999), Jones and Craven (2004), Nover (2005), as well as on review papers published between 1992–2002 in several special issues of Surveys in Geophysics (volumes 13, 17, 18, 20, 23). Similarly to other chapters, it starts with an overview of laboratory measurements of electrical resistivity (conductivity) derived from numerous experimental studies. These data provide the basis for interpretations of electromagnetic (EM) and magnetotelluric (MT) results in terms of the lithospheric electrical conductivity structure. Regional conductivity models are presented for the oceanic and continental lithosphere.