Serendipity, the process of finding something of value initially unsought, has played a prominent role in modern science and technology. These “happy accidents” have spawned new fields of science, broken intellectual and technological barriers, and furnished countless products which have altered the course of human history. In the realm of patent law, one curious aspect of accidental discoveries which has received little attention in the academic literature and the courts is how they mesh with the substantive law of invention. In this Essay, I show that, in certain circumstances, applying conventional doctrines to accidental inventions is theoretically untenable and may result in unfortunate outcomes for the inventor. I offer an alternative approach which is better suited to deal with accidental inventions. Finally, I reflect on how accidental inventions benefit the patent system and the public, including their potential to spur significant follow-on innovation.