Feminism issues are often radically depicted in literary works, especially in a novel. The novelist emphasize these issues to raise the women’s awareness about the oppression that might happen to them. This radical movement happens because they try to create an idealistic society for women. From this premise, radical feminism was born because the previous movement could not undo the women’s oppression as time goes throughout the decades. Adjusting to the patriarchal system, women are often portrayed as unique and unusual to be treated as equal to men. This study is aimed to analyze the radical feminism of Wide Sargasso Sea by Jean Rhys by using Tong’s radical feminism and Petrie and Boggs’ characterization theories. The researcher confirms that Antoinette Cosway’ character is portrayed as a radical feminist through radical libertarians and radical cultural feminists’ ideas in Wide Sargasso Sea novel. These ideas are portrayed through Antoinette ’ androgynous appearance and gender portrayal.