Prince Honore-Gabriel was born in Paris on May 14, 1778, the eldest son of Prince Honore IV of Monaco and Princess Louise Felicite Victoire d'Aumont, Duchesse de Mazarin et de La Meilleraye. He enlisted in a French cavalry regiment when he was 20 years old and worked his way up through the ranks by his own merits until he became an officer on the staff of Marshal Grouchy. He was an exemplary soldier and was cited for his bravery many times. He was wounded in the arm at the great Napoleonic victory in the battle of Hohenlinden which prevented him from seeing action at Austerlitz. He did, however, serve with great distinction at the battles of Jena with Marshal Murat's cavalry corps. Marshal Grouchy related that the Prince had taken a handfull of cavalry and forced the surrender of an entire enemy battalion, recommending him for the star of the Legion of Honor.
When Napoleon was sent into exile the restored King Louis XVIII of France restored the Grimaldis to their places in the French nobility, however, many were afraid that Monagasque independence would not be or that they would be annexed by the Kingdom of Piedmont-Sardinia. Thanks to the clever Prince Talleyrand, however, a clause was inserted into the Treaty of Paris to put Monaco back in order. When Napoleon attempted to restore his empire during the 100 days Monaco was occupied by British troops and so the Grimaldis played no part in the affair.
The ailing Honore IV was unable to return to Monaco and so appointed his brother Joseph to rule on his behalf but Honore-Gabriel protested this and after some struggle he was himself appointed to govern Monaco. On his way to Monaco he actually met with his old commander Napoleon as he was on his way to Paris to seize power at the start of the 100 days. Napoleon asked where he was going and Honore-Gabriel said he was going home to Monaco. Napoleon said he was going home to the Tuileries, but as things unfolded he was not to remain there long.
In 1819, with the passing of his father, Honore-Gabriel became the Sovereign Prince of Monaco as Honore V and inherited a principality beset with problems. The Great Powers of Europe had taken Monaco out of the French sphere of influence and made the principality a protectorate of Piedmont-Sardinia. The government in Turin closed the tobacco plant that Honore III had established and enforced a number of other changes that left Monaco impoverished. Honore V went to Turin to try to reason with the King but, although he was treated with great honor and respect, none of his grievances were addressed. Honore V also had to raise taxes considerably which made him increasingly unpopular. His granting of a monopoly on flour caused a bread shortage but no one had the nerve to voice opposition to him. When liberal movements began to oppose the counterrevolutionary tide of post-Napoleonic Europe some in Monaco thought of joining in but Sardinian troops arrived to crush the potential rebellion in its infancy.
History has tended to record Prince Honore V as a very unpopular and autocratic monarch, however, in reality this is quite unfair and in some ways he was quite progressive. He wished to help his people sincerely and had great sympathy for the poor. His reaction to seeing beggars on the streets was to form state-owned industries and put them to work. Some of the industries he set up included a lace factory and a hat factory. He also had them put to work on farm cooperatives as citrus orchirds had long been a large part of the Monegasque economy. All of this has led some people to regard Prince Honore V as a sort of proto-socialist, though he probably would not have seen it that way.
Prince Honore V died, unpopular and unappreciated (quite unjustly) on October 2, 1841 in Paris. As he was not married and had no children the Monegasque throne passed to his poet-actor brother who became Prince Florestan I of Monaco.