Baroness Marie "Méry" von Bruiningk (August 11, 1818- 22 January, 1853) was an Estonian (Baltic German) democrat, known for her participation in the democratic intellectual debate in the Baltic during the revolution year of 1848.
She was the daughter of Baron Johann Georg von Bruiningk and Maria Dorothea Margareta von Anrep and married Baron Johann Georg von Lieven in 1839. During the 1840s, she was a leading figure in the radical intellectual democratic circle around the von Bruiningk family, and corresponded with Karl Marx and Alexander Herzen.
In the early years after the failure of the revolutions of 1848, a group of German Forty-Eighters and others met in a salon organized by the Baroness and her husband, Ludolf August von Bruiningk, in St. John's Wood, England. The baroness was sympathetic with the goals of the revolutionaries. In addition to Herzen, guests included Carl Schurz, Gottfried and Johanna Kinkel, Ferdinand Freiligrath, Alexander Herzen, Louis Blanc, Malwida von Meysenbug, Adolf Strodtmann, Johannes and Bertha Ronge, Alexander Schimmelfennig, Wilhelm Loewe-Kalbe and Heinrich Bernhard Oppenheim.
In 1851, she and her spouse was forced to leave Russia for political democratic agitation. They settled in Hamburg, where she organized social relief for the political refuges of 1848.