Especially since the second half of the 20th century, important developments in the fields of science, industry and technology have emerged. In parallel with this development, the need to illuminate, especially to the artificial illumination, has increased. Artificial lighting systems have become almost imperative in interior spaces as well as in outdoor spaces such as parks, gardens, streets and city lighting. The most important factor that makes illuminating in outside areas a necessity is the sense of security that people feel safe. On the other side, from the ergonomic point of view, phenomenons such as selectivity and attention-grabbing have made external illumination compulsory. Nowadays, external lighting applications, which is an important part of city lighting, are not done correctly and in a planned way. The city lighting consists of parks, gardens, streets, roads, streets, sports facilities, tourist facilities, exterior lighting and security lighting systems. The problem of light pollution, which has become a big problem nowadays, has come into being when the above mentioned lighting systems are added to the lights that overflow from the internal volumes of the buildings. In the light of this information, the concepts of external lighting, correct lighting and light pollution are covered in detail. The factors that cause light pollution under the heading of outdoor lighting systems have been examined. Finally, the environmental effects of light pollution are determined by using the findings and solution proposal is presented