Why Is Frankenstein A Romantic Novel?

Romanticism is a literary movement which is marked by several key components, many of which are observable in Mary Shelley's Frankenstein.
One element of Romanticism is the belief that imagination is able to lead to a a new and more perfect vision of the world and those who live in it. In this novel, Victor Frankenstein is the idealist who wants to create life from nothing; that is the ultimate ideal and marks victor as a Romantic.
In another sense, Victor's actions demonstrate the Romantic renunciation of science and reason over emotion and nature, “So much has been done, exclaimed the soul of Frankenstein — more, far more, will I achieve; treading in the steps already marked, I will pioneer a new way, explore unknown powers, and unfold to the world the deepest mysteries of creation.” Victor's Romantic quest for the scientific ideal is paralleled by the monster's quest for an emotional connection both with other human beings and his environment.
Nature also plays a significant role in Romanticism and in this novel. Though it may not seem as prominent here as in other works, nature is a significant backdrop for Frankenstein. While this novel is exemplary of the romantic period in that it uses a highly stylized and dramatized frame, more concerned with the realms of the fantastic than those of the real, the fantastic story becomes an allegory for very real emotions and struggles with which romantic writers were deeply preoccupied.
Even the title, Frankenstein; or, the Modern Prometheus, is a reference to a Romantic reliance on mythological allusions. Prometheus stole fire from the gods (he reached too far) and was punished for it, just as Victor overreaches by playing God and creating life and is them punished for it.
In conclusion, Frankenstein is a great reflection of the Romantic Movement. Through the use of emotion, imagination and other aspects of romantic literature, Shelly captivates her readers by creating a new world.