Ferdinand was born in Vienna, a prince of the Koháry branch of the ducal family of Saxe-Coburg-Gotha. He grew up in the cosmopolitan environment of Austro - Hungarian high nobility and also in their ancestral lands in Slovakia and in Germany. The Koháry, descending from a Upper Hungarian noble (now Slovakia) family, were quite wealthy, holding for example the princely lands of Csábrág and Szitnya, in what is now Slovakia. The family's property was also augmented by Clémentine of Orléans' remarkable dowry.

The son of Prince August of Saxe-Coburg and his wife Clémentine of Orléans, daughter of king Louis Philippe I of the French, Ferdinand was a grandnephew of Ernest I, Duke of Saxe-Coburg-Gotha and of Leopold I, first king of the Belgians. His father Augustus was a brother of Ferdinand II of Portugal, and also a first cousin to Queen Victoria, her husband Albert, Prince Consort, Empress Carlota of Mexico and her brother Leopold II of Belgium. These last two, Leopold and Carlota, were also first cousins of Ferdinand I's through his mother, a princess of Orléans. This made the Belgian siblings his first cousins, as well as his first cousins once removed (his father's first cousins). Indeed, the ducal family of Saxe-Coburg-Gotha had contrived to occupy, either by marriage or by direct election, several European thrones in the course of the 19th century. Following the family trend, Ferdinand was himself to found the royal dynasty of Bulgaria. Ferdinand had some ancestry from medieval rulers of Bulgaria, descents from both his mother's and father's side.

The first Knjaz (Prince Regnant) of the III Bulgarian state, Alexander of Battenberg abdicated in 1886, only seven years after he was elected. Ferdinand was elected Knjaz (Prince Regnant) of autonomous Bulgaria by its Grand National Assembly on 7 July 1887 in the Gregorian calendar (the "New Style" used hereinafter). In desperate attempts to prevent Russian occupation of Bulgaria, the throne had been previously offered, before Ferdinand's acceptance, to princes from Denmark to the Caucasus and even to the King of Romania. His accession was greeted with disbelief in many of the royal houses of Europe. Queen Victoria, his father's first cousin, stated to her Prime Minister, "He is totally unfit, ... delicate, eccentric and effeminate .. Should be stopped at once." To the amazement of his initial detractors, Ferdinand generally made a success during the first two decades of his reign.

Bulgaria's domestic political life was dominated during the early years of Ferdinand's reign by liberal party leader Stefan Stambolov, whose foreign policy saw a marked cooling in relations with Russia, formerly seen as Bulgaria's protector.

Ferdinand was rumored to be bisexual throughout his life, but up to middle age, his proclivities for women predominated. Ferdinand entered a marriage of convenience with Princess Marie Louise of Bourbon-Parma, daughter of Roberto I of Parma and Princess Maria Pia of Bourbon-Two Sicilies, on April 20, 1893 at the Villa Pianore in Lucca in Italy, producing four children: Boris III (1894 – 1943), Kyril (1895 – 1945), Eudoxia (1898 – 1985), Nadezhda (1899 – 1958), married Duke Albrecht Eugen of Württemberg. Marie Louise died on 31 January 1899 after giving birth to her youngest daughter. Ferdinand did not think again about marriage until his mother, Princess Clémentine died in 1907. To satisfy dynastic obligations and to provide his children with a mother figure, Ferdinand married Eleonore Caroline Gasparine Louise, Princess Reuss-Köstritz, on 28 February 1908. Ferdinand's regular holidays on Capri, then a famous haunt for wealthy gay men, were common knowledge in royal courts throughout Europe.

Stambolov's fall (May 1894) and subsequent assassination (July 1895) paved the way for a reconciliation of Bulgaria with Russia, effected in February 1896 with the conversion of the infant Prince Boris from Roman Catholicism to Eastern Orthodox Christianity. However, this move earned him the animosity of his Catholic Austrian relatives, particularly that of his uncle, Emperor Franz Joseph I of Austria.

Ferdinand became Tsar (King) of Bulgaria upon that country's declaration of independence from the Ottoman Empire on 5 October 1908 (celebrated on 22 September). The Declaration of Independence was proclaimed by him at the Saint Forty Martyrs Church in Turnovo. It was accepted by Turkey and the other European powers.

Ferdinand was known for being quite a character. On a visit to German Emperor Wilhelm II, his second cousin once removed, in 1909, Ferdinand was leaning out of a window of the New Palace in Potsdam when the Emperor came up behind him and slapped him on the bottom. Ferdinand was affronted by the gesture and the Emperor apologised. Ferdinand however exacted his revenge by awarding a valuable arms contract he had intended to give to the Krupp's factory in Essen to French arms manufacturer Schneider - Cruseot. Another incident particularly occurred on his journey to the funeral of his second cousin, British King Edward VII in 1910. A tussle broke out on where his private railway carriage would be positioned in relation to the heir to the Austro - Hungarian throne, Archduke Franz Ferdinand. The Archduke won out, having his carriage positioned directly behind the engine. Ferdinand's was placed directly behind. Realising the dining car of the train was behind his own carriage, Ferdinand obtained his revenge on the Archduke by refusing him entry through his own carriage to the dining car. On 15 July the same year during a visit to Belgium Ferdinand also became the first head of state to fly in an airplane.

Like many a ruler of an Orthodox land before him, Ferdinand had a "dream of a new Byzantium". In 1912, Ferdinand joined the other Balkan states in an assault on the Ottoman Empire to free occupied territories. He saw this war as a new crusade declaring it, "a just, great and sacred struggle of the Cross against the Crescent." Bulgaria contributed the most and also lost the greatest number of soldiers. The great powers insisted on the creation of an independent Albania. Soon after, Bulgaria attacked its recent allies Serbia and Greece and itself was attacked by Romania and the Ottoman Empire and was defeated. Nevertheless, the Treaty of Bucharest in 1913 gave some territorial gains to Bulgaria. A tiny area of land giving access to the Aegean Sea was secured.

On 11 October 1915, the Bulgarian army attacked Serbia after signing a treaty with Austria-Hungary and Germany which stated that Bulgaria would gain the territory she sought at the expense of Serbia. Ferdinand was not an admirer of German Emperor Wilhelm II (his second cousin once removed) or Emperor of Austria Franz Josef I who he described as "that idiot, that old dotard of a Francis Joseph". But Ferdinand wanted extra territorial gains after the humiliation of the Balkan Wars. This did however mean forming an alliance with his former enemy, the Ottoman Empire. At first the war went well, Serbia was defeated and Bulgaria took possession of most of the disputed territory of Macedonia. For the next two years, the Bulgarian army fought a defensive war against the Allied army based in Greece. Part of the Bulgarian army was involved in the conquest of Romania in 1916.

Then, in the fall of 1918, the Bulgarian army was badly beaten by an attack from the Allied forces in Greece. With his army shattered, Tsar Ferdinand abdicated to save the Bulgarian throne in favour of his eldest son who became Tsar Boris III on 3 October 1918. Under new leadership, Bulgaria surrendered to the Allies and as a consequence, lost not only the additional territory it had fought for in the major conflict, but also the territory it had won after the Balkan Wars giving access to the Aegean Sea.

After his abdication, Ferdinand returned to live in Coburg, Germany. He had managed to salvage much of his fortune and was able to live in some style. He saw his being in exile simply as one of the hazards of kingship. He commented, "Kings in exile are more philosophic under reverses than ordinary individuals; but our philosophy is primarily the result of tradition and breeding, and do not forget that pride is an important item in the making of a monarch. We are disciplined from the day of our birth and taught the avoidance of all outward signs of emotion. The skeleton sits forever with us at the feast. It may mean murder, it may mean abdication, but it serves always to remind us of the unexpected. Therefore we are prepared and nothing comes in the nature of a catastrophe. The main thing in life is to support any condition of bodily or spiritual exile with dignity. If one sups with sorrow, one need not invite the world to see you eat." He was pleased that the throne could pass to his son. Ferdinand was not displeased with exile and spent most of his time devoted to artistic endeavors, gardening, travel and natural history. However, he would live to see the collapse of everything he had held to be precious in life. His eldest son and successor, Boris III, died under mysterious circumstances after returning from a visit to Hitler in Germany in 1943. Boris III's son, Simeon II, succeeded him only to be deposed in 1946, ending the Bulgarian monarchy. The Kingdom of Bulgaria was succeeded by the People's Republic of Bulgaria, under which his sole surviving son, Kyril, was executed. On hearing of his son's death he said, "Everything is collapsing around me." He died a broken man in Bürglaß-Schlösschen on September 10, 1948 in Coburg, Germany, cradle of the Saxe-Coburg-Gotha dynasty. His final will was to be buried in Bulgaria, and for this reason his coffin lies in the crypt of St. Augustin's Roman Catholic Church in Coburg.