Daniel Gabriel Fahrenheit (24 May 1686 – 16 September 1736) was a Dutch-German-Polish physicist, inventor, and scientific instrument maker. He was a pioneer of exact thermometry. He helped lay the foundations for the era of precision thermometry by inventing. The mercury-in-glass thermometer (first practical, accurate thermometer) and Fahrenheit scale (first standardized temperature scale to be widely used). In 1714  Christian von Wolf published a description of one of Fahrenheit’s early thermometers in the Acta eruditorum. Fahrenheit returned to Amsterdam in 1717 and established himself as a maker of scientific instruments

Fahrenheit was born in Danzig/Gdansk. A predominantly German-speaking Hanseatic city in the Pomeranian Voivodeship of the Polish–Lithuanian Commonwealth. But he lived most of his life in the Dutch Republic (1701–1736) and was one of the notable figures in the Golden Age of Dutch science and technology.

So lastly we can say that, Gabriel Daniel Fahrenheit was a German Physicist. He was developed the mercury thermometer in 1714 and he devised temperature scale also.