Ludwig Gaston Klemens Maria of Saxe-Coburg and Gotha (15 September 1870, in Ebenthal – 23 January 1942, in Innsbruck), known in Brazil as Dom Luís Gastão, was a prince of the House of Saxe-Coburg and Gotha-Koháry. He was the fourth son of the German Prince Ludwig August of Saxe-Coburg and Gotha and Princess Leopoldina of Brazil.

Ludwig Gaston was born the youngest of the four sons of Prince Ludwig August of Saxe-Coburg and Gotha and Princess Leopoldina of Brazil. He and his family lived in Brazil until 1889, when troubles with the Brazilian monarchy led the family to move to Europe.

Ludwig went to Wiener Neustadt to study at the Theresian Military Academy, where he successfully graduated in 1892. After that, he was promoted to the rank of Lieutenant of the Fourth Tiroler Jäger-Regiment of the Austro-Hungarian Army in Lienz. On May 1, 1896, Ludwig was given the rank of First lieutenant, and, on March 29, 1900, he was given leadership of the First Tiroler Jäger-Regiment in Innsbruck. On May 1, 1903, he advanced to the rank of Captain.

In Munich, on May 1, 1900, Ludwig Gaston married Princess Mathilde of Bavaria, daughter of the King Ludwig III of Bavaria. Their wedding was hosted by her grandfather, Luitpold, Prince Regent of Bavaria. They had two children:

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