Running is one of the simplest, most accessible, and most popular forms of physical activity worldwide. Besides being a popular sport, running is also a favorite recreational activity among people of all age groups. Some of the benefits that running brings include improved lung capacity, a decrease in resting heart rate, a reduction in the risk of diseases, lower blood pressure, enhanced circulation, an impact on one's body composition, and mental health. The marathon is one of the most well-known and challenging athletic disciplines that test the physical endurance and mental strength of runners. The classic marathon has a length of 42.195 kilometers and falls under the category of long-distance running. It is more than just a race; it is a symbol of strength, perseverance, and human endurance. Running a marathon provides an incredible sense of achievement and pride and represents one of the most prestigious athletic challenges. The aim of this paper is to present the principles of planning training for a marathon. It explains how to set goals, assess the initial condition of a person using appropriate parameters, choose the type of running training when creating a training plan, determine the training load, training intensity, create proper periodization for training, calculate the total training volume, and adjust nutrition and hydration to the training plan in preparation for the race.