This textbook introduces the reader to the study of astrophysics through a journey that spans the fields of physics, mathematics, and technology. Based on the author’s extensive teaching experience, it emphasizes the fundamental observational data and theoretical methods employed for constructing models of stars, galaxies, and large-scale structures in the universe. After an introduction outlining the historical development of universe studies, Part I delves into gravitational theories including basic general relativity and gravitational waves. Part II explores radiation and plasma processes crucial for interpreting observed data and modeling cosmic objects. Part III addresses the observational techniques essential in astrophysics, along with the analysis of astrophysical parameters obtained from photometry and spectroscopy.