Dimitrios Kallergis was a fighter of the Hellenic Revolution of 1821, a lieutenant, politician and one of the main protagonists of the 3rd September Revolution. He was born in 1803 in Rethymno, Crete.

He studied medicine in Paris when he began the Revolution of 1821. He was suspended from his studies and moved to the Peloponnese and participated in the fight. He fought on the side of Karaiskakis and during the battle in Athens, he was caught prisoner by the Turkish Forces. In the summer of 1825, he and his fellow countryman, Emmanuel Antoniades, took over the leadership of the campaign in Crete. On August 2, 200 rebels captured Gramvousa’s fortifications, which in the following months evolved into piracy. The campaign eventually failed, and according to the American philhellene Samuel Chau, Kallergis was suitable for the post of leader. Later, he participated in the campaign of Karaiskakis in Roumeli where he was distinguished.

In 1832 he was promoted to a lieutenant and in 1843 became the colonel of the cavalry. Being then a Colonel, he was probably initiated by Andreas Metaxas and the ambassador of Russia, Katakazis, to the conspiracy against King Otto for the purpose of granting a constitution, and he also made contact with Makrygiannis. He led the 1843 movement, which forced King Otto to remove his Bavarian advisers and give the Constitution to the Greek people.

In 1845, on the occasion of a tension between himself and Queen Amalia, he was forced to leave for exile in London, where he met another exile, Prince Napoleon, the future emperor of France, with whom he became friends. Due to the pressure of the Great Powers, especially France, on the eve of the Crimean War in 1845, he returned to Greece and became Minister for Military in the new Mavrocordatos government. He faced the resentment of King Otto and was resigned the following year.

In 1861 he became an ambassador in Paris, where from there he conceived significantly in the dethronement of King Othon in 1862. In 1866, he returned to Greece, having been appointed equerry of King George. In fact, he proposed to the King to entrust him with the Foreign Ministry, arguing that with the help of the governments of France and Italy he would be able to realize the vision of the Great Idea, but he was not believed by George. In the summer of the same year, he was elected as the Cretan leader of the Revolution, but he could not continue because of health problems.

In January 1867 he was appointed Ambassador of Greece to the United States. During a trip to Paris, he was ill and was forced to return to Greece where he died.