Ferdinand-Victor-Albert-Meinard was born on 24 August 1865, in Sigmaringen, as the second son of Prince Leopold of Hohenzollern, older brother of King Charles I, and Princess Antoinette, Infanta of Portugal.

In 1889, Ferdinand settled in Romania, as the heir presumptive of King Carol I. Article 83 of the Constitution provided that: "in the absence of male descendants of Her Majesty Carol I of Hohenzollern-Sigmaringen, the succession to the throne shall be the eldest of her brothers or of her descendants.".

Both Carol I's older brother, Prince Leopold of Hohenzollern, and his eldest nephew notified that they were renouncing their status as heir to the Romanian throne, so that the succession reverted to Ferdinand, through the "Family Pact" confirmed by the German Emperor himself, Wilhelm I, head of the Hohenzollern family.

Professor VD Paun, from the Saint Sava High School in Bucharest, paints the following portrait of him in a brochure published in Romanian, French and German: "Slim, tall and slender, with dark blue eyes, very gentle... Prince Ferdinand spent his childhood in Dusseldorf - a hotbed of elegant culture. There, His Highness completed his classical secondary education and passed the "Abiturient" exam with honors, corresponding to our baccalaureate... Later, he entered active service, as a second lieutenant in the 1st Imperial Guard Regiment in Potsdam, near Berlin, and after two years of military practice in the barracks and in the field, he went back to school, attending courses in political economy, financial sciences, history, gentile law and Roman law held by famous professors at the Universities of Tubingen and Leipzig."

Significant for understanding the personality of King Ferdinand is also the portrait sketched by Nicolae Iorga: "As a young man, it can be said that Prince Ferdinand's characteristic trait was an extreme modesty mixed with an almost excruciating timidity. Very courteous and polite, he always avoided offending anyone's feelings and gave way even when he knew the subject under discussion better than those he was discussing. He liked solitude, nature and art. Hating any pomp and vain ceremony, he had nevertheless inherited from his mother a shy pride united with a German respect for laws and forms. The most absolute discipline had been the main line of his education and a sense of duty that remained with him throughout his life, helping him unwaveringly to overcome his personal feelings, not allowing them to ever to put on "a middle ground between him and what he had to do. Gentle, without selfishness, those who knew him deeply loved him."

On January 10, 1893, his marriage to Maria of Edinburgh, Princess of Saxe-Coburg-Gotha, took place in Sigmaringen, creating a political alliance of great importance for the Kingdom.

On August 3, 1914, the Crown Council took place in Sinaia, in the old Music Hall of Peleș Castle, and decided on Romania's neutrality in World War I. A few weeks later, on September 27, 1914, also in Peleș, King Carol I died. He was buried in the church of the Curtea de Arges monastery, founded by Neagoe Basarab. Ferdinand became king at the age of 49, swearing before the members of Parliament that he would be a "good Romanian".

In June 1916, the Entente was in difficulty on the Western Front. MV Alexeev, Chief of the General Staff of the Russian Army, and General Joffre, Commander-in-Chief of the French Army, demanded Romania's entry into the war "now or never".

On August 17, 1916, the political convention was signed between Romania, on the one hand, and France, Great Britain, Italy and Russia on the other, through which the Entente recognized the legitimacy of the union of Bukovina, Transylvania and Banat with Romania.

Since 1838 the state of Sigmaringen no longer existed, it had been united with the Prussian possessions and the former sovereign, Charles Anton, grandfather of King Ferdinand, had welcomed this merging of the Hohenzollern heritage of the Rhine into the powerful East German kingdom, for he was a determined partisan of the unification of his people, through struggle and sacrifice. The belief that no one has the right to stop a nation from living within its natural borders was also transmitted to Prince Ferdinand.

As a cruel irony of fate, however, King Ferdinand made use of this creed for the benefit of his adoptive country, thus attracting harsh criticism and sanctions from the head of the Hohenzollern family.

On August 27, 1916, the Crown Council took place in the living room of the Cotroceni Palace, in which King Ferdinand declared: "with a tortured soul I have decided to do my duty to the Romanian people, whose destinies I lead.". On the same day, the Romanian minister in Vienna presented Romania's declaration of war to the Austro-Hungarian foreign minister. From this moment on, only one of N. Filipescu's prophecies could be fulfilled: "Sire, be crowned at Alba-Iulia or die on the plain of Turda."

Overwhelmed in numbers and technology by the enemy, the Romanian army is forced to retreat from Transylvania, Oltenia, Muntenia, Dobrogea, and the royal family and the government take refuge in Iași, which has become the capital of Romania. In the occupied territory, the German authorities claimed that the Kingdom of Romania no longer exists and forbade the mention of the king's name. In May 1917, the political and military leaders in Bucharest decide to "dethrone the Hohenzollerns from Romania".

The outbreak of the Russian Revolution further complicated matters. A coup d'état was planned, through which King Ferdinand and his family would be taken to Russia, to suffer a fate similar to that of the Romanov dynasty. The king decided to go to the front, from where he addressed the soldiers, promising land to the peasants and a wider participation in state affairs. It is representative that volunteers from Transylvania and Bukovina were enlisting in the Romanian army.
After the immense sacrifices at Mărăști, Mărășești and Oituz, in the summer of 1917, Romania finds itself alone in front of the Central Powers, due to Russia's withdrawal, shaken by the revolution and has no other option than to negotiate a peace that King Ferdinand never ratified.

On November 18, 1918, King Ferdinand returned from refuge to Bucharest, at the head of his army, passing under the Arc de Triomphe. During the reception offered that same day to Romanian officials and General Berthelot, the king stated: "When I took over the inheritance of the founder of modern Romania, I promised before the representatives of the nation that I would be a good Romanian; I believe I kept my word. The times were hard, the sacrifices were great, but the reward was brilliant and today I can say with a clear head: before God and my people I have a clear conscience", continuing then: "after Bessarabia and Bukovina, Transylvania, the beautiful cradle of the Romanian people, from where the first voivodes of the Romanian lands dismounted, voted in Alba-Iulia to unite with the Romanian Kingdom".

In 1914, Lesser Romania had 137,000 km², with 7,700,000 inhabitants. In 1918, Greater Romania, with Transylvania, Bukovina, Bessarabia, the Quadrilateral, had 295,000 km², with 17,000,000 inhabitants.

On October 15, 1922, in Alba-Iulia, King Ferdinand I the Unifier was crowned as king of all Romanians "from the Dniester to the Tisa". The ceremony took place in the new and grandiose Orthodox cathedral, built especially for this occasion.

In 1923, a new Constitution was adopted, adapted to the post-war realities after the creation of Greater Romania. It resumed the fundamental principle of constitutional monarchy: "The King reigns, but does not govern."

On July 20, 1927, King Ferdinand I the Integrator or the Loyal, as he was also called, passed away in Pelișor Castle, at the age of 62, following a long illness caused by colon cancer.