Theoretical astrophysics is a science that studies and explains physical phenomena occurring in celestial bodies based on the laws of physics. At the same time, theoretical astrophysics widely uses the mathematical apparatus, which, however, plays only a supporting role. Theoretical astrophysics is a young and rapidly developing science. But its success is already of great importance for all branches of astronomy and for many branches of physics. Theoretical astrophysics is a science that studies and explains physical phenomena occurring in celestial bodies based on the laws of physics. At the same time, theoretical astrophysics widely uses the mathematical apparatus, which, however, plays only a supporting role. Theoretical astrophysics is a young and rapidly developing science. But its success is already of great importance for all branches of astronomy and for many branches of physics. Theoretical astrophysics in the USSR received a particularly wide development. The first Russian-language course in theoretical astrophysics was published in 1939. and was written by the editor of this edition. Over the past 12 years, this young branch of astronomy has had so much success and experienced such profound changes that it was necessary to abandon the idea of simply reworking the old course for a new edition and proceed collectively to compile an entirely new book.