Marguerite Augusta Marie Löwenhielm (27 July 1830 – 19 March 1915) was a French mycologist and author during the 19th and early 20th centuries who studied the effectiveness of new "Americanist" varieties of grapevine in surviving the harmful insect pest Phylloxera.

Introduced to the family trade by her maternal grandmother, Marguerite assisted in producing small batches of wine on a plot of land south of Paris.

While living among the rural farmers in land she had recently inherited, she took a deeper interest in local agricultural science.

In particular, Marguerite was invested in the problem of the Phylloxera, a pest insect which destroyed grape harvests at staggering rates.

Rather than applying more chemicals and pesticides, she sought to introduce hardier strains of grape to the region to combat the Phylloxera.