Streszcz. ang. s. 7. Bibliogr. s. 22

This paper explores evolving gender identity definitions in both social and legal contexts. Traditionally, gender was defined based on visible anatomical features. However, contemporary perceptions acknowledge the significance of gender identity, which may not align with sex assigned at birth. Many legal systems, including the Polish one, still rely on binary gender classifications based on anatomy, while the legal concept of gender identity remains underdefined. The ambiguity regarding legal gender identity calls for a solution that draws from extensive non-legal literature on the topic, to offer a more informed legal understanding. The redefined legal concept of gender should fulfil three key criteria: it should be clear, align with current scientific knowledge, and advance trans rights as well as gender equality. In the paper, three non-legal approaches to defining gender identity - materialist, externalist, and internalist - will be examined; and their potential application in the legal context based on the above-mentioned criteria will be assessed.