Catalina de Erauso's story, La historia de la monja alférez escrita por ella misma / Catalina de Erauso recounts her adventures as a man, her later confession of being a woman and virgin, her pension from the king, and even the Pope's legitimization of her dressing as a man. The author examines this text in terms of its contribution and resistance to the construction of gender in Spain and the Spanish American colonies in the early 17th century. The transatlantic voyages open a space in which the figure of Catalina de Erauso transits from one gender category to another. With an emphasis on the prefix 'trans', reading the text through the lens of the 'transsexual' narrative creates new borders and limits, and accentuates the text as a site of struggle over gender identity. The 'transsexual' narrative can help us see the text not only as a site of transition and combination of social categories, but also for interrupting the binary structure of sex and gender that appears so natural today.