Focusing on the mermaid motif in Henrik Ibsen`s The Lady from the Sea (1888), this study attempts to show 1) how the image of mermaid in the play has evolved from traditional mermaid stories 2) the ways Ibsen problematizes and subverts patriarchism, Christianism, and melodramatic romanticism embedded in the old tales from ancient, medieval, and romantic era and 3) how Ibsen`s unique modernism creates a modern mermaid whose symbolic significance is "overdetermined" by the intersection of romanticism, realism and modernism. First, I overview the genealogy of western mermaid tales/folklores from the sirens in Odyssey to Hans Andersen`s The Little Mermaid to highlight the critical differences between conventional mermaids and Ellida, the heroine of The Lady from the Sea. Then with Ellida, I examine how the dilemma of modern women searching for new identity, new life, new relationship is projected onto this mysterious and miserable woman dubbed by Ibsen as a "half-dead mermaid." Lastly, I re-evaluate the controversial ending of the play to argue that, contrary to the general dismissal of the ending as failure or stopgap, Ibsen intentionally and strategically creates dialectical tension and mutual alienation between myth and realism to emphasize the dangers and limits of our romantic yearning for idealism. Ellida is a modern mermaid who freely chooses to descend from mythic idealism to everyday life/language with which she articulates her fears, envisions new hopes, and takes roots in the ground/reality.