Margareta "Märta" Ulfsdotter, in Norway known as Merete Ulvsdatter (1319-1371), was a Swedish noble and lady in waiting.
She was the daughter of Saint Bridget of Sweden and the head lady in waiting of Margaret I, Queen of Denmark.
After the death of her first spouse, she married the Swedish noble Knut Algotsson.
Between 1366 and 1371, she was the head of the court of Queen Margaret, whom she raised as the foster child with her daughter Ingegerd.
It was said, that she maintained such as superiority and authority over her royal ward, that even after Margaret became queen, she was forced to succumb to Märta's rough treatment.