No. Each numbered entry (Persona 3, 4, 5) features a completely new cast, story, and setting. While there are minor references or easter eggs for longtime fans, the plots are standalone. You can start with any of the modern titles, though Persona 5 Royal is often recommended for newcomers due to its polished mechanics.

Shin Megami Tensei (SMT) is the parent franchise, known for its dark, post-apocalyptic settings, high difficulty, and focus on ideological conflicts between Law and Chaos. Persona is a spin-off series that focuses more on character relationships, high school simulation (Social Links), and Jungian psychology, with a generally more stylish and 'pop' aesthetic.

The Velvet Room is a recurring location in the series that exists 'between mind and matter, dream and reality.' It is hosted by the mysterious Igor and his attendants. Here, the protagonist can manage, summon, and fuse Personas to create stronger allies. The room's appearance changes in each game to reflect the protagonist's state of mind (e.g., an elevator, a limousine, a prison cell).

Persona 5 Royal is the definitive version of Persona 5. It adds a significant amount of new content, including a new party member (Kasumi Yoshizawa), a new school semester (the 'Third Semester'), new story events, gameplay improvements, and new areas to explore in Tokyo. It is widely considered the superior way to experience the game.

Persona games are hybrid experiences that combine a full-length JRPG dungeon-crawler with a day-by-day life simulator. You play through a full calendar year of a student's life, managing time between studying, hanging out with friends, working jobs, and saving the world. This detailed day-to-day progression naturally leads to playtimes often exceeding 100 hours.