Heteronormativity is an ideology that presumes that heterosexuality is, and should be, the only, the dominant, or the taken-for-granted sexuality for all. In the present thesis, I aim to develop a cognitive understanding of romantic love, as a heteronormative construct. In Chapter 1, I explore a history of psychological research on romantic love to develop my argument that researchers have typically taken heterosexuality as the default in research on romantic love. In Chapter 2, I expand on this argument and postulate that concepts (particularly social concepts) can encode heteronormative ways of thinking about the world. The next four chapters focus on exploring the cognitive construction of romantic love, and explore if participants’ take heterosexual as the default when thinking about romantic love. Heterosexual participants were found to construct romantic love differently depending of task demands. When the task appeared difficult, participants responded with heterosexual as the default (Chapters 3 and 5). In contrast, when the task appeared easy participants responded equally across sexuality conditions (Chapters 4 and 5). Lesbians, gay men and bisexual individuals were found to construct very different understandings of romantic love from heterosexual individuals (Chapter 6). The following two chapters explore how different understandings of romantic love influence perceptions of romantic relationships. In Chapter 7, I observed that participants draw upon a cognitive construction of romantic love when developing an understanding of a romantic relationship. Building on this, in Chapter 8, I found that the prototype of romantic love only predicted the perceived validity of a heterosexual relationship. In the conclusion (Chapter 9), I propose that heterosexual people may construct an understanding of romantic love on the basis of heterosexuality, which biases the perceptions of same-sex relationships. However, this construct of romantic love is not absolute, and can change.