Introduction: Prolonged progress can occur in the first and second stages of labour and may contribute to a negative birth experience. However, previous studies have mainly focused on quantitative aspects or overall birth experience, and little is known about women's experiences of a prolonged passive second stage. Objective: To describe the lived experiences of a prolonged passive second stage of labour in nulliparous women. Methods: A qualitative study was conducted with 15 nulliparous women with a passive second stage lasting three hours or more. Data were analysed using thematic analysis based on descriptive phenomenology. Results: The analysis resulted in four themes: “An unknown phase” that entailed remaining in a phase that the women lacked an awareness of. “Trust and mistrust in the body's ability” represents the mindset for vaginal birth as well as feelings of powerlessness and self-guilt. The theme “Loss of control” included experiences of frustration, fatigue, and having to deny bodily instincts. “Support through presence and involvement” signifies support through the midwife's presence in the birthing room, although there were also descriptions of emotional or physical absence. Conclusions: The findings contribute to the understanding of prolonged labour based on women's lived experiences and add to the body of knowledge about the prolonged passive second stage. This study highlights that women need support through information, presence, and encouragement to remain in control. It can be beneficial during birth preparation to include knowledge about the passive second stage together with unexpected or complicated situations during birth, such as prolonged labour.