The term "Captain General" started to appear in the 14th century, with the meaning of Commander in Chief of an army (or fleet) in the field, probably the first usage of the term General in military settings. A popular term in the 16th and 17th centuries, but with various meanings depending on the country, it became less and less used in the 18th century, usually substituted with, simply, General or Field Marshal; and after the end of the Napoleonic Wars it had all but disappeared in most European countries, except Spain and former colonies. See also Feldhauptmann ("field captain"). Other ranks of general officer, as distinct from field officer, had the suffix "general"; e.g. major general, lieutenant general, brigadier general, colonel general.
Republic of Venice
In the Republic of Venice, it meant the commander in chief in war time. The captain general of the land forces was usually a foreign mercenary or condottiere, but the Venetian navy was always entrusted to a member of the city's patriciate, who became Captain general of the Sea. It is at least documented since 1370 and was used up to the fall of the Republic of Venice in 1797.
From 30 June to 22 October 1513, Catherine of Aragon held the titles Governor of the Realm and Captain General of the King's Forces as Queen Regent of England. It was first attested in the 1520s as the title for the permanent Commander in Chief of the Armies. The title was commonly used in the 17th century. In the 18th century, the office was held by the Duke of Marlborough (1702 to 1711, and again 1714 to 1717), and by the Duke of Ormonde, 1711 to 1714, and by the Duke of Cumberland 1745.
The rank remains in Scottish use of the Royal Company of Archers.
The title appeared, as in some other countries, linked to the head of state in his military capacity. Her Majesty Queen Elizabeth II is Captain General of the Honourable Artillery Company and also of the Royal Regiment of Artillery, an appointment similar to Colonel-in-Chief in other regiments. Her husband Prince Philip, Duke of Edinburgh, was Captain General Royal Marines from 1953 to 2017. Prince Harry was appointed Captain General Royal Marines on 19th December 2017.
New South Wales
From 1787 (the year before the arrival in Australia of the First Fleet) to 1837, the Governor of New South Wales was referred to as Captain-General.
In Prussia a Generalkapitän was the commander of the
castle guard and
In Rhode Island, the Governor holds two different military titles. According to Article IX, section 3 of the Rhode Island Constitution, the Governor holds the titles of "captain-general" and "Commander-in-Chief" 
In Connecticut, the state Constitution of 1965 states that the Governor is also the Captain General of the Connecticut State Militia.
The 1786 Constitution of Vermont, which became effective when Vermont was an independent country and continued in effect for two years after Vermont's admission to the Union in 1791, says "The Governor shall be captain-general and commander-in-chief of the forces of the State, but shall not command in person, except advised thereto by the Council, and then only as long as they shall approve thereof." The language remained in the 1793 Constitution of Vermont.
Maurice of Nassau received the title of "Captain General of the Union" and "Admiral General" in 1587, which became hereditary – like the Stadtholder title, to the Orange-Nassau family, until taken away by the States General in 1786.
By the late 15th century, the rank, besides the usual meaning of commander-in-chief in the field, was also linked to the highest commander of specialized military branches (artillery, royal guards, etc.), usually signaling the independence of that particular corps.
No later than the fall of Granada (1492) the title was conferred also on officers with full jurisdiction of every person subject to fuero militar (military obligations) in a region. Those officers usually also acted as commanders for the troops and military establishments in their area and, as time passed, those duties (and the title) were mostly united in the highest civilian authority of the area. During the period of Spanish rule in much of Latin America there were several Captaincies of the Spanish Empire. The military post of captain general as highest territorial commander lasted in Spain until the early 1980s.
In the late 17th or very early 18th century, a personal rank of captain general was created in the Spanish Army (and Navy) as the highest rank in the hierarchy, not unlike the Marechal de France. When wearing uniform, the kings used captain general insignia. Valeriano Weyler, Governor General of Cuba in 1896–97 during the period preceding the Spanish–American War, held the rank. Briefly abolished by the Second Spanish Republic, it was restored during the regime of Francisco Franco in 1938; Franco himself was the only officer of this rank. Later King Juan Carlos I (1975), Agustín Muñoz Grandes (1956) and Camilo Alonso Vega (1972) were promoted while on active duty; a few posthumous promotions and promotions of retired officers to this rank were also made. In 1999, the rank was reserved to the reigning monarch.
The evolution of the title in the Spanish Navy is parallel to that of the army.
During the 16th and 17th century the two main naval captain general posts were Capitán-General de la Armada de la Mar Oceana and Capitán-General de Galeras, roughly CIC for the Atlantic and the Mediterranean respectively.
A peculiar usage of the term captain general arose in the Spanish Navy of the 16th century. A capitán-general was appointed by the king as the leader of a fleet (although the term 'squadron' is more appropriate, as most galleon fleets rarely consisted of more than a dozen vessels, not counting escorted merchantmen), with full jurisdictional powers. The fleet second-in-command was the 'almirante' (admiral), an officer appointed by the capitan-general and responsible for the seaworthiness of the squadron. One captain-general that sailed under the Spanish flag that is now well known was Ferdinand Magellan, leader of the first fleet to sail around the world.
Under the Nationalist regime of 1939–1975, the only holder of the rank of capitán general de la armada was the Caudillo, Generalísimo Francisco Franco.
The rank of captain general of the Air Force is held only by HM King Felipe VI.
The title was given, in 1508, to the commander-in-chief of the Ordenanças (the territorial army of the crown).
During the Portuguese Restoration War, after 1640, the "Captain-General of the Arms of the Kingdom", became the commander-in-chief of the Portuguese Army, under the direct authority of the War Council and the King. In 1762 the post of the captain-general was replaced by the title marechal-general – fieldmarshall-general.
Like in the Army, the Capitão-General da Armada Real (Captain-General of the Royal Navy) was the commander-in-chief of the Portuguese Navy in the 17th and 18th centuries.
The title has been only sporadically used in France. During the 17th century, and for a short while, a rank between Lieutenant General and Marshal of France of this denomination was created. The king of France was the Captain General of the Army, but was represented in the field by lieutenant generals who commanded in his absence.
Kingdom of Bavaria
In the former Kingdom of Bavaria, the generalkapitän was the leader of the royal Hartschier guard. The position was associated with the highest class ranking in the Hofrangordnung (court order of precedence).
During the time of the Papal States the title of Captain General of the Church was given to the de facto commander-in-chief of the Papal Army. It existed parallel to the office of Gonfalonier of the Church, which was a more ceremonial position than a tactical military command position. Both offices were abolished by Pope Innocent XII and replaced with the office of Flag-bearer of the Holy Roman Church.
Czech, Poland, Lithuania and Ukraine
The term "Captain General" as Hetman (the word from the German Hauptmann "Capitan") is a political title from Eastern Europe, historically assigned to military commanders. It was the title of the second-highest military commander (after the monarch) in 15th- to 18th and 20th-century.