A galleass was a type of warship - a hybrid that combined the sails and armament of a galleon with the maneuverability of the oared galley. While never quite matching up to the full expectations for its design, the galleass nevertheless remained in use during the 16th and 17th centuries.
Galleasses were higher, larger and slower than regular galleys. They had up to 32 oars, each worked by up to five men. They usually had three masts, and unlike galleys, proper forecastles and an aftcastles. Much effort was made in Venice to make galleasses as fast as possible to compete with regular galleys. The gun deck usually ran over the rowers' heads, but there are also pictures showing the opposite arrangement. Galleasses usually carried more sails than galleys and had far more firepower; a galley caught in a galleasses broadside was in great danger, since it exposed to a large amount of gunfire. Relatively few galleasses were built—one disadvantage was that, being more reliant on sails, their position at the front of the galley line at the start of a battle could not be guaranteed.
In the 16th century, a type of light galleass, called the frigate, was built in southern European countries to answer the increasing challenge posed by the North African-based Barbary pirates in their fast galleys.
In the Mediterranean, with its less dangerous weather and fickle winds, both galleasses and galleys continued to be in use, particularly in Venice and the Ottoman Empire, long after they became obsolete elsewhere. Later, "round ships" and galleasses were replaced by galleons and ships of the line which originated in Atlantic Europe. The first Venetian ship of the line was built in 1660.