Екатерина I
Matryona Ivanovna Balk (née Modesta Mons; fl. 1718), was a Tsardom of Russian courtier. She was a lady-in-waiting and confidant of Catherine I of Russia, Ober-Hofmeisterin of Tsarevna Catherine Ivanovna of Russia and sister of Anna Mons. She was accused in 1718 for having assisted the empress in her love affair with Willem Mons.