He is best known for his position as foreign minister of France under his cousin Napoleon III and for his diplomatic efforts presiding over the Congress of Paris, which created peace in the Crimean War and laid the base for modern international law of the sea with the Paris Declaration Respecting Maritime Law.

Alexandre Florian Joseph Colonna Walewski was born on May 4, 1810, at Walewice, near Warsaw, to Countess Maria Walewska, the Polish noblewoman and mistress of Napoleon Bonaparte.

To satisfy an old family prejudice, I was held at the font by two beggars, which was supposed to bring me luck..." [1] In 2013, published scholarship comparing DNA haplotype evidence taken from Emperor Napoleon, from his brother King Jérôme Bonaparte's descendant Charles, Prince Napoléon and from Colonna-Walewski's descendant indicated Alexandre's membership in the genetic male-line of the imperial House of Bonaparte.

On June 15, while in Königsberg Napoleon signed letters patent confirming Alexandre's title, and his new coat of arms combined the insignias of the Walewski and Laczynski families.

After his defeat at Waterloo, Marie Walewska and Alexandre were present at Malmaison to bid farewell to Napoleon before his exile to Saint Helena.

[11] Upon the accession of Louis-Philippe d'Orléans to the French throne in 1830, Walewski was dispatched to Poland, later the same year being entrusted by the leaders of the Polish November Uprising of 1830 as a diplomatic envoy to the Court of St James's.

He is said to have collaborated with the elder Dumas on Mademoiselle de Belle-Isle and a comedy of his, L'Ecole du monde, was produced at the Theâtre Français in 1840.

[11] Later that year the prime minister of France Thiers, also a man of letters, became patron to one of Walewski's papers, Le Messager des Chambres, before sending him on a mission to Egypt.

Under Guizot's government Walewski was posted to Buenos Aires to liaise with the British Ambassador, John Cradock, 1st Baron Howden.

Prince Louis Napoleon's accession to power in France as Napoleon III furthered his career with postings as envoy extraordinary to Florence, Grand Duchy of Tuscany, and the Kingdom of the Two-Sicilies before London (1851–55), where he was charged with announcing the coup d'état to the prime minister, Lord Palmerston.

The latter treaty did contain an important novelty in international law, creating the possibility for nations that were not involved in the establishment of the agreement, to become a party by acceding to the Declaration afterwards.

[11] Walewski was made a Duke of the Empire ad personam in 1866,[15] was elected a member of the Académie des beaux-arts, appointed Grand-Cross of the Imperial Order of the Legion of Honour and made a Knight og the Sovereign Military Order of Malta, also receiving the Gold Cross of Virtuti Militari.