This dissertation presents a study of the shared themes and parallel narrative structures of a set of stories about extraordinary birth. Stories about extraordinary birth form a universal story-type that displays widespread and striking similarities in narrative traditions throughout the world. Stories of this nature are typically told about various types of important persons, such as heroes, kings, gods, and saints, and have most frequently been treated within the context of the "heroic biography" pattern. Because of how well-attested this type of story is in all narrative traditions, a comparison of birth narratives from different Indo-European mythologies offers an ideal case study in the comparison and reconstruction of aspects of the Proto-Indo-European mythological system. While my primary focus is on stories from Indo-European sources, and particularly from Celtic, Greek, and Indic myth, several non-Indo-European examples of this type of narrative are also included in my discussion. The stories under consideration here can be defined as stories that describe a birth (often including conception and gestation) that in some way or another, and to a greater or lesser extent, deviates from what one would consider a "normal" or "ordinary" birth, from a social or biological standpoint. Stories about extraordinary births tend to emulate the progression of normal birth to some degree, though at every step the possibility for the distortion, inversion, and violation of the natural order is present. Because these stories mimic actual birth, a specific narrative structure is inherent to stories of this type and provides the starting point for a comparative exploration of these stories in the cultures and contexts in which they appear.