This book introduces the general theory of relativity and includes applications to cosmology. The book provides a thorough introduction to tensor calculus and curved manifolds. After the necessary mathematical tools are introduced, the authors offer a thorough presentation of the theory of relativity. Also included are some advanced topics not previously covered by textbooks, including Kaluza-Klein theory, Israel's formalism and branes. Anisotropic cosmological models are also included. The book contains a large number of new exercises and examples, each with separate headings. The reader will benefit from an updated introduction to general relativity including the most recent developments in cosmology.

Øyvind G. Grøn is a professor emeritus at the University of Oslo and Oslo Metropolitan University. His work mainly focuses on general relativity, gravitation and cosmology. He received his Candidatus realium from the Institute of Geophysics, the University of Oslo in 1973 and his Ph.D. from the Institute of Physics, University of Oslo in 1990. He was honored with the research prize of Illustrert Vitenskap and the King’s Gold Medal in 1988, the research prize of Oslo University College in 2004, the popularization prize of Oslo University College in 2009, and the Universe outstanding reviewer award in 2025. He has been a member of the Royal Norwegian Society of Sciences and Letters since 2005, an honorary member of the Norwegian Astronomical Society and of the Norwegian Physical Society since 2010 and 2023, respectively. He has served as an editorial board member of scientific journals—European Journal of Physics, Universe, Physica Scripta—and contributed to Fra Fysikkens Verden as an editor.

Sigbjørn Hervik is a professor at the Department of Applied Mathematics, the University of Stavanger. His work focuses on Riemannian geometry, Lorentzian geometry, Lie group and algebras, homogeneous spaces, relativity, cosmology from the mathematical aspects, alternative theory of gravity and classification issues for exact solutions in general relativity. He received his Ph.D. from Cambridge University in 2004. After his professional experience as a postdoc fellow at Dalhousie University in Canada, he was appointed to the current position in 2008. He has been teaching mathematics at all levels. He has received several research grants including a Toppforsk grant from the Research Council of Norway regarding interdisciplinary research between differential geometry and general relativity. He was honored with the Olav Thon prize for teaching excellence—a prestigious national teaching prize—in 2022.