Charles III de Bourbon, Count de Montpensier, then Duke of Bourbon (17 February 1490 – 6 May 1527) was a French military commander, governor, prince of the royal blood and rebel during the early Italian Wars. The son of Gilbert de Bourbon and Clara Gonzaga, he was born into a junior branch of the royal house of France. The early death of his father and elder brother meant that he became the comte de Montpensier (count of Montpensier) in 1501. He then secured a very advantageous marriage in 1505 to Suzanne de Bourbon, the heiress to the senior line of the house of Bourbon. By this means he became the greatest feudal lord in the French kingdom. He participated in the expeditions of king Louis XII seeing combat at Genoa in 1507 and at the famous battle of Agnadello in 1509. In 1512, he was established as the governor of Languedoc, and in the final years of Louis XII's reign he would fight the Spanish in Navarre and the English in Picardy.

With the death of Louis XII in 1515, he would receive great honour from his successor Francis I when he was established as the Constable of France, the greatest office of the crown, which made him the head of the royal army. Francis was keen to see the French reconquer the duchy of Milan and undertook a campaign to this end in the first year of his reign. The duc de Bourbon (duke of Bourbon) had a key role to play in this campaign, leading the royal vanguard in the victory of Marignano. With Milan reconquered, Bourbon was established as the military governor of the duchy, though he would only hold this charge until May 1516. Back in France, Bourbon had limited involvement in the affairs of the next few years, joining the King for various occasions. At this time he and Suzanne were attempting to produce an heir, but their children all died young.

In 1521, France entered war with the Holy Roman Empire which was led by the young new emperor Charles V. In the campaign on the northern frontier of the kingdom, Bourbon was denied the role of commander of the vanguard which was his by right, embittering him. During this year, his wife Suzanne also died. This created two crises of relations with the French crown, the one because of his plans for remarriage, the other because of her extensive inheritance, which she had willed to him. King Francis, and his mother Louise disputed her will, arguing the inheritance rightfully defaulted to them. A lengthy legal battle began, which was prejudiced when Francis accepted his mother doing homage for most of the lands that were disputed. In August 1523, all the disputed lands were sequestered from Bourbon. Concurrent to this legal battle, Bourbon began exploring betraying the French crown in favour of service to Charles V, entering a treaty with the Emperor in July 1523. With the sequestering of his lands, Bourbon broke with the French crown and fled the French kingdom, joining with the Imperial commanders in Italy.

Now a commander for the Holy Roman Emperor, Bourbon helped rebuff a new French attempt to secure Milan in 1523. He then followed this up by leading an invasion of the French province of Provence, though this invasion stalled out before the walls of Marseille and he was forced to retreat back into Italy. The royal French army pursued him into the peninsula, but was delivered a crushing defeat at the battle of Pavia at which Bourbon fought, and at which the French king was made prisoner. Bourbon and Charles V looked to extract heavy concessions from the French, with Bourbon hoping to gain a marriage with the sister of the Emperor Eleanor, regain all his lands in France as a sovereign lord, and be made the comte de Provence.

The treaty of Madrid would grant him some of these concessions but not all, and upon his release, Francis would honour none of the concessions made to the duc de Bourbon. Instead, the French king entered into a new alliance to oppose the Holy Roman Emperor known as the league of Cognac. Bourbon took charge of the effort to combat this league in Italy. He conquered Milan for the Emperor, who had offered to make him the duke of Milan and then led a mutinous army south to Rome which he put to siege on 6 May 1527. He would be killed trying to scale the walls, but the city was successfully taken, and subject to a brutal sack. After his death, he was posthumously declared guilty of various crimes in France. The legal dispute over the lands confiscated from him would not be entirely settled until the reign of Charles IX over thirty years later.

Charles de Bourbon was born on 17 February 1490, the son of Gilbert de Bourbon, the comte de Montpensier (count of Montpensier) and Clara Gonzaga. Charles' father Gilbert would serve as the French viceroy of Naples for the king Charles VIII but would die of the plague after his army was forced to surrender in November 1496. Through his mother Clara, Charles was the grandson of the marquis of Mantua, ruler of an Italian polity. Gilbert and Clara had married in 1481.

Charles was the second son of the marriage. His elder brother Louis de Bourbon, succeeded their father as comte de Montpensier before his early death in August 1501. He also had a younger brother, François de Bourbon, who would become duc de Châtellerault before his early death in 1515. Charles also had an elder sister Louise de Bourbon who would live until 1561 and who married the prince de La Roche-sur-Yon. Their union would form the foundation of the second house of Bourbon-Montpensier after the extinction of the first with the death of Charles in 1527. Another sister of Charles, Renée would marry the duc de Lorraine in 1515, thereby binding the house of Bourbon with that of Lorraine.

The House of Bourbon descended from Robert de Bourbon, comte de Clermont, a younger son of king Louis IX. Several branches of the Bourbon family existed at the start of the sixteenth-century: the Bourbon-Beaujeu (otherwise known as Bourbon proper) which became extinct with the death of Suzanne de Bourbon, Charles' wife, in 1521, the Bourbon-Montpensier (of which Charles de Bourbon was a member) and the Bourbon-Vendôme.