An Introduction to Solar Radiation is an introductory text on solar radiation, with emphasis on the methods of calculation for determining the amount of solar radiation incident on a surface on the earth. Topics covered include the astronomical relationship between the sun and the earth; thermal radiation; the solar constant and its spectral distribution; and extraterrestrial solar irradiation. This book is comprised of 12 chapters and begins with an overview of the trigonometric relationships between the sun-earth line and the position of an inclined surface, followed by a discussion on the characteristics of blackbody radiation. The next chapter focuses on the solar constant and its spectral distribution, paying particular attention to extraterrestrial solar spectral irradiance and the sun’s blackbody temperature. Subsequent chapters explore extraterrestrial and radiation incident on inclined planes; the optics of a cloudless-sky atmosphere; solar spectral radiation and total (broadband) radiation under cloudless skies; and solar radiation arriving at horizontal surfaces on the earth through cloudy skies. The ground albedo and its spectral and angular variation are also described, along with insolation on inclined surfaces. The last chapter is devoted to instruments for measuring solar radiation, including pyrheliometers and pyranometers. This monograph will serve as a useful guide for energy analysts, designers of thermal devices, architects and engineers, agronomists, and hydrologists as well as senior graduate students.