Costantino Nigra was a philologist, poet, diplomat and Italian politician.
He was born on 11 June 1828 at Villa Castelnuovo - today Castelnuovo Nigra in the province of Turin - by Ludovico Nigra and Anna Caterina Revello. The father worked as a local ceruse and took part first as a soldier of Napoleon Bonaparte's army and following the insurrectional uprisings of 1821; his mother Anna Caterina was related to Gian Bernardo De Rossi (1742-1831), an orientalist much appreciated internationally. Constantine was very attached to his parents and his siblings, especially his younger brother Michelangelo, who lost an eye at a tender age due to a reckless game of Constantine.
He completed his first studies in Bairo and later in Ivrea where he completed the second school cycle. In 1845, thanks to a scholarship, he was able to enroll in the Faculty of Law of the University of Turin, despite his great interest in poetry and literature.
During the university studies he did not hide (1848) the support for the war conflict in Piedmont with the Austrian imperial power, so much so that he decided to enroll in the body of the Bersaglieri students, as a volunteer. He participated in the battles of Peschiera del Garda, Santa Lucia and Rivoli, where he was wounded in one arm. Already the following year he returned to fight, witnessing the defeat of Novara. Resumed his studies after the brackets, he was able to graduate in law at the University of Turin.
Nigra brought to the attention of the Italians a new form of poetry, the epic narrative.
He served in the Ministry of Foreign Affairs since 1851 and was appointed secretary to Prime Minister Massimo D'Azeglio and later to Camillo Cavour, who accompanied the 1856 Paris Congress as Head of Cabinet.
Two years later, in 1858, he was sent on a secret mission to Paris to realize the hypothesis of a decided alliance between Platobius between Napoleon III and Cavour and designing the war between the Kingdom of Sardinia and the Austrian Empire. He played a decisive role in Italian foreign policy for completing the process of unification of Italy after Cavour's death in 1861. He later became Italian ambassador in Paris (1860), St. Petersburg (1876), London (1882) and finally in Vienna (1885).
During his tenure in Paris he contributed to the negotiations that led, thanks to the consent of Napoleon III, to the conclusion of the Italo-Prussian Alliance of 1866. In 1870, ambassador to Paris, after the defeat of Napoleon III to Sedan, the emperor himself he was taken prisoner. He remained the only friend of the empress Eugenia de Montijo, named regent. Since the people had risen by proclaiming the Republic, Nigra helped her to escape and to save herself. 
In 1887 he refused the post of Foreign Minister, offered to him by King Umberto I of Savoy. In 1882 and in 1890 he was appointed senator of the Kingdom of Italy. He will also be awarded the Supreme Order of the Santissima Annunziata.
Exponent of Freemasonry, Nigra had been regularized in the Ausonia loggia of Turin in February 1860. He was elected Grand Master of the Grand Orient of Italy on 3 October 1861 a few months after Cavour's death, but, in November of the following year, he renounced the assignment. Among the reasons that may have led to leave the great mastery, there is the fact that Nigra remained ambassador of Italy in France at a time when the Italian masonry, Republican and Garibaldian, increased its distance from the Second Empire. In his letter of renunciation, Nigra nonetheless diplomatically signaled his willingness to represent the GOI in the Grand Orient of France (GODF). Among other reasons, there was perhaps embarrassment for a sincere Cavourian monarchist to lead an institution that in the 1960s would become increasingly republican.