How do autocratic ruling parties gain power? What predicts their durability and how they fall? This article introduces the Autocratic Ruling Parties Dataset, the first comprehensive data set on the founding origins, modes of gaining and losing power, ruling tenures, and other characteristics of autocratic ruling parties. It covers all ruling parties in the world from 1940 to 2015. Contrary to common assumptions, most ruling parties are not created by sitting dictators, but follow a range of paths to power that influence their style and duration of rule. To illustrate the data’s uses, the article confirms that ruling parties stabilize autocracies. Further, parties’ origins and histories matter, with revolutionary and foreign-imposed parties the most durable and parties empowered through elections the least durable. By recognizing ruling parties’ heterogeneity, histories, and potential autonomy from individual dictators, the data can contribute to open questions on autocratic politics, regime stability, and democratization.