Prince Rainer Maria Joseph Florian Ignatius Michael Gabriel Raphael Gonzaga of Saxe-Coburg and Gotha, in German: Rainer Maria Joseph Florian Ignatius Michael Gabriel Raphael Gonzaga, Prinz von Sachsen-Coburg und Gotha (4 May 1900, in Pola – after 7 January 1945).

The deaths of his older brother August (1908) and his father (1922), made him the fourth in the Roman Catholic line of Saxe-Coburg-Gotha princes to inherit the legacy of the House of Koháry.

In addition to being in the line of succession to the Coburg throne, he possessed one of the largest fortunes in Hungary, one of the constituent realms within the Habsburg Empire, whose reign, however, he saw come to an end, along with that of the Dukes of Saxe-Coburg and Gotha, in 1918.

Even after the fall of the German and Austro-Hungarian monarchies, he retained ownership of most of the vast Koháry domains, which continued to generate a princely income.

In Munich on 15 December 1930 Prince Rainer married, firstly, Johanna Károlyi de Károly-Patty (17 September 1906 – 17 November 1992).