The primary factor contributing to the rise of nationalism in 19th-century Europe was the growing demand for self-determination among various ethnic and cultural groups. The Romantic movement energized nationalist sentiments by celebrating folk culture, history, and language, promoting the idea that nations should be based on a common identity. Additionally, the decline of empires, such as the Ottoman and Austrian Empires, provided the impetus for various nationalist movements seeking independence and unification, profoundly reshaping the political map of Europe.