Adolphus Frederick VI, Grand Duke of Mecklenburg-Strelitz

Adolphus Frederick VI (17 June 1882 – 23 February 1918) was the last reigning grand duke of Mecklenburg-Strelitz.

Adolphus Frederick George Ernest Albert Edward of Mecklenburg was born in Neustrelitz, the third child and eldest son of Adolphus Frederick V, Grand Duke of Mecklenburg, and his wife, the former Princess Elisabeth of Anhalt. He attended a gymnasium school in Dresden and later studied jurisprudence in Munich and served in the Prussian army. Adolphus Frederick became heir apparent to the Grand Duchy, with the title of Hereditary Grand Duke of Mecklenburg-Strelitz, following the death of his grandfather Grand Duke Frederick William on 30 May 1904.

Adolphus Frederick and his brother Duke Karl Borwin are said to have agreed that Adolphus Frederick could devote his life to painting, while Karl Borwin would marry and continue the dynasty; but this agreement could never be realised, as Karl Borwin was killed during a duel with Count George Jametel in 1908. Adolphus Frederick was subsequently reported to be engaged to various European princesses, including Princess Viktoria Luise of Prussia, the only daughter of the German Emperor William II and his consort, Augusta Victoria of Schleswig-Holstein.

He succeeded as Grand Duke on the death of his father on 11 June 1914, just a few weeks before the outbreak of World War I. Adolphus Frederick was reported to have married morganatically with attempts made to force him to divorce his wife and conduct an equal marriage, but he was reported to have refused. Recent research has disproven claims that the operatic soprano Mafalda Salvatini, an Italian by birth but raised mainly in Paris, and a star at the Berlin State Opera and the Deutsche Oper Berlin, had been his mistress from 1908 until his suicide in 1918 and that her two sons, Charles E. (Horst) Gérard and the set and costume designer and painter Rolf Gérard, were illegitimate children of the Grand Duke.

On 23 February 1918 at Neustrelitz, Adolphus Frederick committed suicide. This left Mecklenburg-Strelitz facing a succession crisis, as the only surviving member of the Strelitz line, Duke Charles Michael of Mecklenburg, had served in the Russian military (in opposition to German and allied forces) and had indicated in 1914 that he wished to renounce his rights to the throne of Mecklenburg-Strelitz; at Adolphus Frederick's request, Charles Michael later agreed to defer any renunciation until the matter arose. There was also a morganatic male-line relative, Duke Charles Michael's nephew George, Count of Carlow.

Because Charles Michael was in Russia, Grand Duke Friedrich Franz IV of Mecklenburg-Schwerin became regent for Mecklenburg-Strelitz and remained such until the end of the German monarchies in 1918, when the government in Strelitz declared the end of the regency. Friedrich Franz IV received confirmation from Charles Michael that he wished to renounce his succession rights, although this only arrived in 1919, after the abolition of the monarchies and the establishment of the Free State of Mecklenburg-Strelitz.

Adolphus's fortune had been amassed by his grandfather and was estimated at 30 million marks. In his will, he left his entire fortune to Friedrich Franz IV of Mecklenburg-Schwerin's second son, Duke Christian Ludwig (1912–96). He did this on the condition that Christian agree to become Grand Duke of Mecklenburg-Strelitz and take up residence in Neustrelitz; otherwise the inheritance would be reduced to 3 million marks.

• 17 June 1882  – 30 May 1904: His Highness The Hereditary Prince of Mecklenburg-Strelitz
• 30 May 1904  – 11 June 1914: His Royal Highness The Hereditary Grand Duke of Mecklenburg-Strelitz
• 11 June 1914  – 23 February 1918: His Royal Highness The Grand Duke of Mecklenburg, Prince of Wenden, Schwerin and Ratzeburg, Count of Schwerin, Lord of the Lands of Rostock and Stargard