Internet addiction (IA) or problematic use of the Internet (PUI) refers to excessive engagement in online activities despite negative consequences in daily life. IA can include excessive online gaming, compulsive online shopping, excessive pornography use, cyberchondria, excessive social media use, and many other forms. First described in the late 1990s, IA is increasingly recognized for its significant impact on mental health and its growing prevalence. The prevalence of IA varies widely, from 0.8% to 26.7% of the general population, largely due to differing diagnostic criteria and clinical thresholds used. Male sex and younger age are recognized risk factors. Eastern countries show the highest prevalence. IA can be conceptualized as a behavioral addiction, characterized by spending a great deal of time online, persisting in the behavior despite negative consequences, experiencing withdrawal symptoms, and the impact on daily functioning. Research has focused on its psychiatric comorbidities, given the high rates of co-occurrence with other mental disorders. Mood disorders, anxiety, substance use, attention-deficit/hyperactivity disorder (ADHD), impulse control disorders, and obsessive-compulsive disorder (OCD) are among the most common. In summary, IA is an emerging condition necessitating further research to comprehend its full impact on mental health. Challenges in diagnostic definition and effective treatment remain. Ongoing research aims to elucidate the complexities of IA, ultimately enhancing prevention and treatment strategies for this emerging condition.