Margaret (or Margaretha) of Soissons (died ca. 1350) was the only daughter of Hugh, Count of Soissons, and Johanna of Argies. In 1306 she succeeded her father as Countess of Soissons.
Margaret was married to John of Beaumont, son of John II, Count of Holland. Margaret and John had five children:
Upon their marriage, John became Count of Soissons, jure uxoris.
Dormay, C., Histoire de la ville de Soissons et de ses rois, ducs, comtes et gouverneurs, Soissons, 1664 (available on Google Books)