Ferdinand I (modern Bulgarian: Фердинанд I; contemporary Bulgarian: Фердинандъ I), born Ferdinand Maximilian Karl Leopold Maria of Saxe-Coburg and Gotha, was the ruler of Bulgaria from 1887 to 1918, first as knyaz (prince regnant, 1887–1908) and later as tsar (king, 1908–1918).
On 5 October 1908 (celebrated on 22 September), Ferdinand proclaimed Bulgaria's de jure independence from the Ottoman Empire (though the country had been basically independent since 1878). He also proclaimed Bulgaria a kingdom, and assumed the title of tsar - a deliberate nod to the rulers of the earlier Bulgarian states. The Bulgarian 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.
On 11 October 1915, the Bulgarian army attacked Serbia after signing a treaty with Austria-Hungary and Germany stating that Bulgaria would gain the territory it sought at the expense of Serbia. Ferdinand was not an admirer of German Emperor Wilhelm II (his second cousin once removed) or Austrian Emperor Franz Josef I whom he described as "that idiot, that old dotard of a Francis Joseph". However, Ferdinand wanted additional territorial gains after the humiliation of the Balkan Wars. This also entailed forming an alliance with his former enemy, the Ottoman Empire.
During the initial phase of World War I, the Kingdom of Bulgaria achieved several decisive victories over its enemies and laid claim to the disputed territories of Macedonia after Serbia's defeat. For the next two years, the Bulgarian army shifted its focus towards repelling Allied advances from nearby Greece. They were also partially involved in the 1916 conquest of neighboring Romania, now ruled by another Ferdinand I, who was also Ferdinand's second cousin once removed.
To save the Bulgarian throne, Tsar Ferdinand abdicated 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.
|One Stotinka 1912||20,000,000||БЪЛГАРИЯ СЪЕДИНЕНИЕТО ПРАВИ СИЛАТА|
|Two Stotinki 1912||40,000,000||БЪЛГАРИЯ СЪЕДИНЕНИЕТО ПРАВИ СИЛАТА|
|Fifty Stotinki 1912||2,000,000||Portrait by Rudolf Marschall||ФЕРДИНАНДЪ I ЦАРЬ НА БЪЛГАРИТѢ|
|Two Leva 1912||1,000,000||Portrait by Rudolf Marschall||ФЕРДИНАНДЪ I ЦАРЬ НА БЪЛГАРИТѢ|
|Ten Stotinki 1912||13,000,000||БЪЛГАРИЯ СЪЕДИНЕНИЕТО ПРАВИ СИЛАТА|
|One Lev 1912||2,000,000||Portrait by Rudolf Marschall||ФЕРДИНАНДЪ I ЦАРЬ НА БЪЛГАРИТѢ|
|Twenty Stotinki 1912||10,000,000||БЪЛГАРИЯ СЪЕДИНЕНИЕТО ПРАВИ СИЛАТА|
|Twenty Leva 1912||75,000||Portrait by Rudolf Marschall||ФЕРДИНАНДЪ I ЦАРЬ НА БЪЛГАРИТѢ|
|Five Stotinki 1912||14,000,000||БЪЛГАРИЯ СЪЕДИНЕНИЕТО ПРАВИ СИЛАТА|
|One Hundred Leva 1912||5,000||Portrait by Rudolf Marschall||ФЕРДИНАНДЪ I ЦАРЬ НА БЪЛГАРИТѢ|
|Two Leva 1913||500,000||Portrait by Rudolf Marschall||ФЕРДИНАНДЪ I ЦАРЬ НА БЪЛГАРИТѢ|
|One Lev 1913||3,500,000||Portrait by Rudolf Marschall||ФЕРДИНАНДЪ I ЦАРЬ НА БЪЛГАРИТѢ|
|Fifty Stotinki 1913||3,000,000||Portrait by Rudolf Marschall||ФЕРДИНАНДЪ I ЦАРЬ НА БЪЛГАРИТѢ|
|Five Stotinki 1913||20,000,000||БЪЛГАРИЯ СЪЕДИНЕНИЕТО ПРАВИ СИЛАТА|
|Twenty Stotinki 1913||5,000,000||БЪЛГАРИЯ СЪЕДИНЕНИЕТО ПРАВИ СИЛАТА|
|Ten Stotinki 1913||20,000,000||БЪЛГАРИЯ СЪЕДИНЕНИЕТО ПРАВИ СИЛАТА|
|Two Leva 1916||2,286,008||Portrait by Rudolf Marschall||ФЕРДИНАНДЪ I ЦАРЬ НА БЪЛГАРИТѢ|
|One Lev 1916||4,568,696||Portrait by Rudolf Marschall||ФЕРДИНАНДЪ I ЦАРЬ НА БЪЛГАРИТѢ|
|Fifty Stotinki 1916||4,562,051||Portrait by Rudolf Marschall||ФЕРДИНАНДЪ I ЦАРЬ НА БЪЛГАРИТѢ|
|Five Stotinki 1917||53,200,000||БЪЛГАРИЯ СЪЕДИНЕНИЕТО ПРАВИ СИЛАТА|
|Ten Stotinki 1917||59,100,000||БЪЛГАРИЯ СЪЕДИНЕНИЕТО ПРАВИ СИЛАТА|
|Twenty Stotinki 1917||40,000,000||БЪЛГАРИЯ СЪЕДИНЕНИЕТО ПРАВИ СИЛАТА|