Mental health smartphone applications have become widely available for self-management and support, offering young people new pathways for help-seeking. Despite their increasing popularity, little is known about how app accessibility, content, and features vary across countries, languages, and cultural contexts. This study aimed to systematically examine these differences by drawing on data from the available app stores. Both the Apple App Store and Google Play Store were searched across seven European countries (Croatia, France, Ireland, Poland, Portugal, Serbia, and Türkiye) using four keywords: mental health, psychological wellbeing, self-help, and stress. App results were screened through redefined inclusion and exclusion criteria, and the included apps were systematically characterized based on their aims, features, and linguistic accessibility. Over 900 apps were initially identified, and 171 met the inclusion criteria. The most commonly encountered apps were structured journaling and meditation apps, and most were partially paid and primarily available in English, highlighting a predominance of commercially oriented apps and a limited availability of local-language apps and minimal cultural adaptation. Together, the findings underscore the need for research and policy to prioritize cross-country accessibility, particularly for non-English speaking youth, to ensure equitable access to digital mental health resources.