Marie Sophie Gräfin von Brühl (Countess Marie Sophie von Brühl; 3 June 1779 - 28 January 1836) was a member of the German von Brühl noble family originating in Thuringia.
She was born in Warsaw. On 17 December 1810 she married Carl von Clausewitz, whom she first met in 1803. She published several of his books in the years 1832-34 after his death in 1831, including his most famous one, On War. Additionally, von Brühl wrote a preface to On War.
Her paternal grandfather was Heinrich von Brühl, a German statesman.
Regarding personal names: Gräfin is a title, translated as Countess, not a first or middle name. The male form is Graf. In Germany, however, since 1919 Gräfin/Graf are no titles any more but part of the surname, thus following the given name(s) and not to be translated.