Henry IV (13 December 1553 – 14 May 1610) was King of France from 1589 to 1610 and (as Henry III) King of Navarre from 1572 to 1610. He was the first monarch of the Bourbon branch of the Capetian dynasty in France. His parents were Queen Jeanne III and King Antoine of Navarre.

As a Huguenot, Henry was involved in the Wars of Religion before ascending the throne in 1589. Before his coronation as king of France at Chartres, he changed his faith from Calvinism to Catholicism and, in 1598, he enacted the Edict of Nantes, which guaranteed religious liberties to the Protestants and thereby effectively ended the civil war. One of the most popular French kings, both during and after his reign, Henry showed great care for the welfare of his subjects and displayed an unusual religious tolerance for the time. He was assassinated by a fanatical Catholic, François Ravaillac. Henry was nicknamed Henry the Great (Henri le Grand), and in France is also called le bon roi Henri ("the good king Henry") or le Vert galant ("the Green gallant"), a reference to both his dashing character and his attractiveness to women. In English he is most often referred to as Henry of Navarre. He also gave his name to the Henry IV style of architecture, which he patronised. He is the eponymous subject of the royal anthem of France, "Marche Henri IV".

Henri de Bourbon was born in Pau, the capital of the French province of Béarn. Although baptised as a Roman Catholic, Henry was raised as a Protestant by his mother Jeanne d'Albret; Jeanne declared Calvinism the religion of Navarre. As a teenager, Henry joined the Huguenot forces in the French Wars of Religion. On 9 June 1572, upon Jeanne's death, he became King Henry III of Navarre.

It had been arranged, before Jeanne's death, that Henry would marry Margaret of Valois, daughter of Henry II and Catherine de' Medici. The wedding took place in Paris on 19 August 1572 on the parvis of Notre Dame Cathedral. On 24 August, the Saint Bartholomew's Day Massacre began in Paris and several thousand Protestants who had come to Paris for Henry's wedding were killed, as well as thousands more throughout the country in the days that followed. Henry narrowly escaped death thanks to the help of his wife. He was made to live at the court of France, but escaped in early 1576; on 5 February of that year, he abjured Catholicism at Tours and rejoined the Protestant forces in the military conflict.

Henry of Navarre became the legal heir to the French throne in 1584 upon the death of Francis, Duke of Alençon, brother and heir to the Catholic King Henry III, who had succeeded Charles IX in 1574. Because Henry of Navarre was the next senior agnatic descendant of King Louis IX, King Henry III had no choice but to recognise him as the legitimate successor. Salic law disinherited the king's sisters and all others who could claim descent by the distaff line. However, since Henry of Navarre was a Huguenot, this set off the War of the Three Henries phase of the French Wars of Religion. The third Henry, the Duke of Guise, pushed for complete suppression of the Huguenots, and had much support among Catholic loyalists. This set off a series of campaigns and counter campaigns culminating in the battle of Coutras. In December 1588, Henry III had Henry I of Guise murdered, along with his brother, Louis Cardinal de Guise. This increased the tension further and Henry III was assassinated shortly thereafter by a fanatic monk.

Upon the death of Henry III on 2 August 1589, Henry of Navarre nominally became the king of France. But the Catholic League, strengthened by support from outside, especially from Spain, was strong enough to force him to the south. He had to set about winning his kingdom by military conquest, aided by money and troops bestowed by Elizabeth I of England. Henry's Catholic uncle, Charles, Cardinal de Bourbon, was proclaimed king by the League, but the Cardinal himself was Henry's prisoner. Henry was victorious at Ivry and Arques, but failed to take Paris. After the death of the old Cardinal in 1590, the League could not agree on a new candidate. While some supported various Guise candidates, the strongest candidate was probably Isabella Clara Eugenia, the daughter of Philip II of Spain, whose mother Elisabeth had been the eldest daughter of Henry II of France. The prominence of her candidacy hurt the League, which became suspect as agents of the foreign Spanish. Nevertheless Henry remained unable to take control of Paris.

On July 25, 1593, with the encouragement of the great love of his life, Gabrielle d'Estrées, Henry permanently renounced Protestantism, thus earning the resentment of the Huguenots and of his former ally, Queen Elizabeth I of England. He was said to have declared that Paris vaut bien une messe ("Paris is well worth a mass"), but this may have been recently refuted. His entrance into the Roman Catholic Church secured for him the allegiance of the vast majority of his subjects and he was crowned King of France at the Cathedral of Chartres on 27 February 1594. In 1598, however, he declared the Edict of Nantes, which gave circumscribed toleration to the Huguenots.

Henry's first marriage was not a happy one, and the couple remained childless. Henry and Margaret had separated even before Henry had succeeded to the throne in August 1589, and Margaret lived for many years in the château of Usson in Auvergne. After Henry became king of France, it was of the utmost importance that he provide an heir to the crown in order to avoid the problem of a disputed succession. Henry himself favoured the idea of obtaining an annulment of his marriage to Margaret, and taking as a bride Gabrielle d'Estrées, who had already borne him three children. Henry's councilors strongly opposed this idea, but the matter was resolved unexpectedly by Gabrielle's sudden death in the early hours of 10 April 1599, after she had given birth prematurely to a stillborn son. His marriage to Margaret was annulled in 1599, and he then married Marie de Médicis in 1600. For the royal entry of Marie into Papal Avignon, 19 November 1600, the Jesuit scholars bestowed on Henry the title of the Hercule Gaulois ("Gallic Hercules"), justifying the extravagant flattery with a genealogy that traced the origin of the House of Navarre to a nephew of Hercules' son Hispalus.

Henry IV proved to be a man of vision and courage. Instead of waging costly wars to suppress opposing nobles, Henry simply paid them off. As king, he adopted policies and undertook projects to improve the lives of all subjects, which made him one of the country's most popular rulers ever. A declaration often attributed to him is:

This egalitarian statement epitomises the peace and relative prosperity Henry brought to France after decades of religious war, and demonstrates how well he understood the plight of the French worker or peasant farmer. Never before had a French ruler even considered the importance of a chicken or the burden of taxation on his subjects, nor would one again until the French Revolution. After generations of domination by the extravagant Valois dynasty, which had caused the French people to pay to the point of starvation for the royal family's luxuries and intrigue, Navarre's charisma won the day. Henry's forthright manner, physical courage and military successes also contrasted dramatically with the sickly, effete languor of the last tubercular Valois kings, as evinced by his blunt assertion that he ruled with "weapon in hand and arse in the saddle" (on a le bras armé et le cul sur la selle).

During his reign, Henry IV worked through his faithful right-hand man, the minister Maximilien de Béthune, duc de Sully (1560 – 1641), to regularise state finance, promote agriculture, drain swamps to create productive crop lands, undertake many public works, and encourage education, as with the creation of the Collège Royal Henri-le-Grand in La Flèche (today Prytanée Militaire de la Flèche). He and Sully protected forests from further devastation, built a new system of tree-lined highways, and constructed new bridges and canals. He had a 1200 m canal built in the park at the royal Château at Fontainebleau (which can be fished today), and ordered the planting of pines, elms and fruit trees. The king renewed Paris as a great city, with the Pont Neuf, which still stands today, constructed over the Seine river to connect the Right and Left Banks of the city. Henry IV also had the Place Royale built (since 1800 known as Place des Vosges), and added the Grande Galerie to the Louvre. More than 400 metres long and thirty-five metres wide, this huge addition was built along the bank of the Seine River, and at the time was the longest edifice of its kind in the world. King Henry IV, a promoter of the arts by all classes of people, invited hundreds of artists and craftsmen to live and work on the building's lower floors. This tradition continued for another two hundred years, until Emperor Napoleon I banned it. The art and architecture of his reign have since become known as the Henry IV style.

King Henry's vision extended beyond France, and he financed several expeditions of Pierre Dugua, Sieur de Monts and Samuel de Champlain to North America that saw France lay claim to Canada. During the reign of Henry IV, various enterprises were set up to develop trade to faraway lands. In December 1600, a company was formed through the association of Saint-Malo, Laval and Vitré to trade with the Moluccas and Japan. Two ships, the Croissant and the Corbin, were sent around the Cape in May 1601. One was wrecked in the Maldives, leading to the adventure of François Pyrard de Laval, who managed to return to France in 1611. The second ship, onboard which was François Martin de Vitré, reached Ceylon and traded with Acheh in Sumatra, but was captured by the Dutch on the return leg at Cape Finisterre. François Martin de Vitré was the first Frenchman to write an account of travels to the Far East in 1604, at the request of Henry IV, and from that time numerous accounts on Asia would be published.

From 1604 to 1609, following the return of François Martin de Vitré, Henry IV of France developed a strong enthusiasm for travel to Asia and attempted to set up a French East India Company on the model of England and the Netherlands. On 1 June 1604, he issued letters patent to Dieppe merchants to form the Dieppe Company, giving them exclusive rights to Asian trade for 15 years. No ships were sent, however, until 1616. In 1609, another adventurer, Pierre-Olivier Malherbe returned from a circumnavigation and informed Henry IV of his adventures. He had visited China and in India had an encounter with Akbar.

Even before Henry's accession to the throne, the French Huguenots were in contact with the Moriscos in plans against Habsburg Spain in the 1570s. Around 1575, plans were made for a combined attack of Aragonese Moriscos and Huguenots from Béarn under Henri de Navarre against Spanish Aragon, in agreement with the king of Algiers and the Ottoman Empire, but these projects foundered with the arrival of John of Austria in Aragon and the disarmement of the Moriscos. In 1576, a three-pronged fleet from Constantinople was planned to disembark between Murcia and Valencia while the French Huguenots would invade from the north and the Moriscos accomplish their uprising, but the Ottoman fleet failed to arrive. After his crowning, Henry IV continued the policy of Franco-Ottoman alliance and received an embassy from Mehmed III in 1601. In 1604, a "Peace Treaty and Capitulation" was signed between Henry IV and the Ottoman Sultan Ahmet I, giving numerous advantages to France in the Ottoman Empire. An embassy was sent to Tunisia in 1608, led by Savary de Brêves.

Although he was a man of kindness, compassion and good humor, and was much loved by his people, Henry was the subject of several murder attempts: by Pierre Barrière in August 1593 and by Jean Châtel in December 1594.

King Henry IV was ultimately assassinated in Paris on 14 May 1610 by a Catholic fanatic, François Ravaillac, who stabbed the king to death while his coach's progress was stopped by a cart. Henry was buried at the Saint Denis Basilica. Hercule de Rohan, duc de Montbazon was with him when he was killed; Hercule himself was wounded but survived.

His widow, Marie de' Medici, served as Regent for their 9-year-old son, Louis XIII, until 1617.

The reign of Henry IV had a lasting impact on the French people for generations afterwards. A statue of him was built in his honor at the Pont Neuf in 1614, only four years after his death. Although this statue - as well as those of all the other French kings - was torn down during the French Revolution, it was the first to be rebuilt, in 1818, and it still stands today on the Pont Neuf. A cult surrounding the personality of Henry IV emerged during the Restoration. The restored Bourbons were keen to downplay the contested reigns of Louis XV and Louis XVI and instead emphasised the reign of the benevolent Henry IV. The song "Vive Henri IV" ("Long Live Henry IV") was used during the Restoration as an unofficial anthem of France, played in the absence of the king. In addition, when Princess Caroline of Naples and Sicily (a descendant of him) gave birth to a male heir to the throne of France, seven months after the assassination of her husband Charles Ferdinand, duc de Berry by a Republican fanatic, the boy was conspicuously called Henri, in reference to his forefather Henry IV. The boy was also baptised in the traditional way of Béarn/Navarre, with a spoon of Jurançon wine and some garlic, as had been done when Henry IV was baptised in Pau (although this custom had not been followed by any Bourbon king after Henry IV).