Ottoman naval forces during the late fifteenth and sixteenth centuries often included corsairs as components of the military forces that were employed by the state in its rivalry with other naval powers for control of the Mediterranean Sea. Individuals could during their careers be employed by the state as corsairs, while later during a war or campaign they might be given an official position in the Ottoman military hierarchy. Because the division between official and supplementary forces was porous, the extent of the contribution of corsair forces to the success of Ottoman seapower can be overstated. In 1543 Suleyman commissioned his admiral, Hayreddin Pasha, to lead the Ottoman fleet to the western Mediterranean shores to aid Francis I of France against their common enemy, Charles V. Hayreddin commanded the official Ottoman fleet, which was financed by the Sultan. Corsairs also accompanied the fleet during parts of this campaign and participated in some of the military actions. Despite the fact that they were not part of the official navy, they were nevertheless part of the effective naval military force. Although, the official fleet wintered at Toulon at the expense of the Ottoman and French governments, the corsairs had to fend for themselves and spent the winter in North Africa. This paper will analyze the composition of the Ottoman naval forces during this expedition to delineate the relationship between the official and unofficial naval forces of the Ottoman Empire that contributed to the development of effective Ottoman naval power during the sixteenth century. In addition to this expedition, other comparable campaigns will be analyzed to determine the corsair contribution to Ottoman naval forces. The campaign of 1543-44 will be studied using Ottoman chronicles such as the Tarih-i Feth-i ?iklo? ve Estergon ve ?stunibelgrad by Nasuh Matrakç? and Gazavat-? Hayreddin Pa?a by Muradi, which includes documents. In addition, western sources that recount the size and composition of the fleet will also be analyzed such as Jérome Maurand, Itinéraire de Jérome Maurand d’Antibes à Constantinople 1544 and Henry, “Documents relatifs au séjour de la flotte turque de Barberousse à Toulon, pendant l’hiver de 1543 a 1544.” By analyzing Ottoman naval campaigns of the first half of the sixteenth century this paper will determine the extent to which Ottoman naval power relied on the recruitment of non-state forces, as well as compare this to similar practices by European powers during this period.