Celestial mechanics is one of the most ancient science. It is dedicated to the study of the motion of planets, moons, asteroids, comets and other celestial bodies. It probably started when humans discovered that some special stars differentiate from the others in the sense that they move on the celestial sphere. Currently, it is responsible for successfully guiding spaceships to distant objects in our solar system aiming to explore them. As an introduction to this Focus Issue in Celestial Mechanics, we make here a historical overview of developments in this area and present the articles that comprise this special issue.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)