Image source : The Sonnet by William Mullready, 1998.
Romanticism is a movement in the literature of virtually every country of Europe, the United States, and Latin America that lasted from about 1750 to about 1870, characterized by reliance on the imagination and subjectivity of approach, freedom of thought and expression, and an idealization of nature. The term romantic first appeared in 18th-century English and originally meant "romancelike"—that is, resembling the fanciful character of medieval romances. [Quoted from: http://www.lycaeum.org/~maverick/romantic.htm].
The earliest examples of Romantic literature started in Germany and the most crucial and remarkable literary figure was Goethe. His novel, The Sorrows of Young Werther (1774), about a young and a sensitive artist was much popular throughout Europe. He used local folklore and myth as subjects for his poetry. He became an inspirational source for a sense of German nationalism in the decades prior to a unified Germany. After that, the French Revolution in the late 18th century brought about romantic ideals such as liberty, freedom, and national pride.
Throughout the 19th century, Romanticism dominated English literature and romantic poetry, in particular, became the most significant work of the period. William Wordsworth, Samuel Taylor Coleridge, William Blake, Lord Byron, Percy Bysshe Shelley, and John Keats are notable Romantic poets from Britain. Nature, religious fervor, emotional response to beauty, and Ancient Greek aesthetics, are some of the common themes in their work. Romantic novels were much popular in 19th century Britain. Romanticism was well present in the form of the Gothic novel, which exploited emotions like romantic love and fear. Mary Shelley's Frankenstein (1818), Charlotte Bronte's Jane Eyre (1847), and Emily Bronte's Wuthering Heights (1847) are some of the well known examples.
In the young United States, Romantic literature flourished remarkably. You can see the work of Washington Irving, Edgar Allen Poe, and Nathaniel Hawthorne written in the Gothic vein. Moreover, Ralph Waldo Emerson, and Henry David Thoreau put greater emphasis on the natural beauty and man's identity as a natural being. Later on, such themes echoed in the work of poets like Walt Whitman. The literature of other countries also got influenced by Romanticism. In France, the novels of Stendhal and Victor Hugo are often characterized as part of the Realist movement but they certainly have some Romantic influence. If we talk about Eastern Europe, Russian writers Mikhail Lermontov, and Alexander Pushkin were some of the practitioners of the Romantic Movement. [Quoted from: http://www.zeroland.co.nz/romantic_literature.html].