Naval power is a crucial element of state power, yet existing naval data sets are limited to a small number of states and ship types. Here we present 147 years of naval data on all the world's navies from 1865 to 2011. This country-year data set focuses on warships with ship-based weapons capable of using kinetic force to inflict damage on other structures or peoples. After identifying a country's active naval forces, we create a measure of naval power based on the aggregate tonnage of the active ships. Additionally, we create count variables for ship types such as aircraft carriers or battleships. This article introduces the country-year data, describes variables of interests for use in country-year, dyadic, or systemic studies, and suggests potential questions of interest scholars could explore using the naval power data set.