Watching romantic movies is considered haram in Islam. This is because they often contain ‘awrahs (parts of the body that should be covered) and immoral actions, which are accompanied by music. Constantly exposing oneself to feelings and fantasies that cannot be lawfully fulfilled can be harmful spiritually, emotionally, and physically. Therefore, it is not permissible to engage in such activities.

And Allah knows best.

Sources:

• IslamQA
• About Islam
• Ask Imam