Smartphones are the technological devices of our age that are constantly developing and their use is becoming more widespread every day. Nowadays, many transactions from shopping to banking activities, playing mobile games and taking photos can be done easily with smart phones. Smart phones, which make positive contributions to daily life, attract great attention by individuals of all age groups, especially young people. According to Newzoo's report, the number of smartphone users, which was 3.5 billion in 2020, is expected to reach 4.1 billion in 2023. Smartphones, which are preferred by almost everyone for reasons such as being easily portable, providing fast access in transactions, ease of use and sometimes a status indicator, can pose a risk for addiction when used uncontrolled. Smartphone addiction, although not yet clearly defined; It can manifest itself with symptoms such as constantly checking the phone, feeling restless when staying away, withdrawing, mood changes, not being able to control the duration of use, disruption in daily life due to problematic use, constant desire to use and pleasure from use. According to the behavioral approach, if a person takes pleasure from a behavior or avoids negative emotions with this behavior, this situation turns into a habit in the individual. Uncontrollable and frequently repetitive habits carry a risk for addiction. Smartphone addiction, in addition to being a behavioral disorder, can cause many physical, social and psychological problems. Problematic use of the smartphone; decrease in sleep duration and quality, height, wrist, thumb and shoulder pain , dry eye syndrome, and eye fatigue, decreased physical activity, as well as depression, social phobia, loneliness, and decreased academic performance can bring along many psychological and social problems. It can be said that poor sleep quality is one of the primary problems that may occur in the problematic use of the smartphone, and it negatively affects both daily life and the health of the individual. Especially at night and in the pre-sleep period, the use of smartphones adversely affects sleep quality as it causes arousal due to the blue light it emits, shortens the sleep duration and disrupts the circadian rhythm. A study stated that exposure to blue light 1 hour before sleep reduces the duration of deep sleep and causes sleep quality to deteriorate. Another study stated that leaving smartphones out of the bedroom improved sleep quality. It is stated that poor sleep quality negatively affects the individual physically and psychologically, causes performance losses and increases the risk of accidents. In studies conducted with students, it was stated that poor sleep quality negatively affects academic performance, while good sleep quality increases academic performance. A study conducted with adolescents stated that poor sleep quality was associated with low self-esteem and increased levels of anxiety and depression. Nurses, who serve almost all of the society, have an important role in defining risky health behaviors and planning and implementing appropriate interventions for behavior change. For this reason, nurses need to make an effort to find the most appropriate behavior change approaches for the individual. Today, the Transtheoretic Model (TTM) is widely used to improve the behavior change process in the individual and to achieve the most effective health behavior change. TTM, which aims at the initiative suitable for the change phase of the individual, is used as a guide that facilitates behavior change. TTM is a cognitive-behavioral model that accepts that any behavioral change in an individual does not happen all at once, but that behavior change includes different stages and processes. The model, which was first used in smoking cessation programs, was later used in many areas such as exercise, sun protection, reducing the amount of excess fat in the diet, weight control, condom use, supporting mammography screening, widespread drug use, coping with stress and quitting substance abuse. Traditional behavior change models have an understanding that does not take into account the change stage of the individual or accepts that all individuals have the same level of readiness for behavior change. it is stated that the initiatives applied without considering the individual's readiness level for behavior change develop resistance to behavior change. In TTM, behavior change; It is defined as a gradual, continuous and dynamic structure. Change in traditional behaviorist approaches; In this model, change focuses on helping individuals willingly make behavioral change and understanding the change process. In other words, it does not classify individuals only according to whether they can perform a certain behavior, but also according to the stages passed in the behavior change process. While TTM creates a roadmap in change, there are also approaches that contribute to and accelerate this change and support the individual who thinks about change. One of these approaches, which is used more frequently in addicted individuals, is the "motivational interview" method. Motivational interviewing is very effective in gaining positive health behaviors and changing negative health behaviors and can be an effective communication technique for nurses in providing behavior change. Motivational interviewing as defined by Miller; "It is a client-centered interview form in which suggestions are made to provide behavior change by helping individuals discover and solve their problems". In motivational interviewing, the expert is the consultant, but the consultant does not assume the role of the knower, is not ready before the client, does not impose his own thoughts, wherever the client is, the consultant is directed there. Solving problems in motivational interviewing is the client's job, not the counselor's. Direct persuasion, aggressive confrontation and discussion are the conceptual opposites of motivational interviewing. Motivational interviewing is accompaniment and non-judgmental acceptance. In the interview, the energy of the client should be used and his desire for change should be revealed. motivational interview; It is a partnership-friendship relationship rather than an expert-recipient role. The counselor should respect the client's autonomy, freedom to make choices and bear the consequences. Nurses, who have very important roles and duties in the provision of health services to the society, undertake important duties not only at the point of care for the sick individual, but also in the fight against situations that threaten public health. In particular, public health nurses interact not only with patients but also with the entire society they serve, as they work in primary health care institutions. Smartphone addiction and the problems it causes are an important public health problem that threatens the whole society and especially young individuals. In the solution of this problem, it is also among the duties of the public health nurse to provide the individual with healthy lifestyle behaviors instead of problematic behavior. As in all risky behaviors that threaten public health, the public health nurse provides consultancy services to the society as a requirement of education and consultancy in smart phone addiction and informs the society about the problems that may arise with the trainings it will organize. Based on this information, the reason for the selection of nursing students in the research universe; To raise awareness among students and contribute to public health, since nursing students are candidates to provide health services to the society, they are role models for the society with their healthy lifestyle behaviors, they interact with individuals from all parts of the society in business life, and there are institutions that provide service on addiction among their work areas. decided with consideration. Another important factor in the selection of the research population is that, considering smartphone addiction, especially young individuals are more at risk for addiction and the problems that may arise from addiction, as they are more intertwined with technology and use smartphones more. According to the data of the Turkish Statistical Institute (TUIK) for 2021, it is stated that the rate of smartphone usage is higher for people with a university level education. In studies conducted in our country and abroad, approximately 50% of university students expressed themselves as smartphone addicts. Considering that being away from family and being more active in social life increases the need for communication among university students, it can be said that they are at higher risk for smartphone addiction when it is considered that they are not under family supervision since most of them reside in dormitories or student houses. In studies evaluating the smart phone usage habits of university students; It has been concluded that they use it for 6 hours or more, the purpose of their use is communication and access to social media, they use it more intensively in the evening and late at night, and they always keep it with them in the pre-sleep period. In studies examining the results of smartphone addiction in university students, results such as decrease in sleep quality, decrease in academic performance, depression, anxiety, muscle and joint pain were reached. It is thought that the university years, which are an important period for the development and maintenance of health protective and preventive behaviors, will both increase the health responsibility of the students and protect them from health-threatening behaviors with the healthy lifestyle behaviors to be gained in this period. It is seen that studies on smartphone addiction are generally descriptive studies aimed at determining the situation. Almost all of the intervention studies that could be reached were carried out in Far East countries and different intervention methods were used. In intervention studies aimed at preventing smartphone addiction; motivational interviewing, cognitive behavioral therapy, laughter therapy, sand play therapy, literacy therapy, peer relations development program, music therapy , mind-bending meditation program, mind-body exercise, journaling, and art therapy have been reached. In line with all this information, our study was planned to determine the effect of TTM and motivational interview-based online intervention program on smartphone addiction and sleep quality levels in nursing students who are in the risk group for smartphone addiction.