Princess Helena of Denmark (also Helene Valdemarsdatter) (c. 1180 – 22 November 1233 in Lüneburg) was heiress of Garding and Lady of Lüneburg.
Helena was daughter of Valdemar I of Denmark and Sophia of Minsk and sister of Ingeborg of Denmark, Queen of France.
In the summer of 1202 in Hamburg, Helena married Lord William of Lüneburg. Helena and William had a son, the future Duke, Otto I, The Child. After the early death of her husband, Duke William, in 1213, his brother, Emperor Otto IV, took over the reign of Lüneburg, as regent for Otto the Child. Otto was appointed heir of the allodial property of the Guelphs by his uncle Henry the Elder.
Helena died in 1233 and was buried in the Benedictine monastery of St. Michael in Lüneburg.