Princess Helena of Waldeck and Pyrmont (1899–1948)

Princess Helena of Waldeck and Pyrmont (Helena Bathildis Charlotte Marie Friederike; 22 December 1899 – 18 February 1948) was a member of the House of Waldeck and Pyrmont. She was the daughter of Friedrich, Prince of Waldeck and Pyrmont, and Princess Bathildis of Schaumburg-Lippe.

Born in Arolsen, Germany, Princess Helena married Nikolaus, Hereditary Grand Duke of Oldenburg, son of Frederick Augustus II, Grand Duke of Oldenburg, and Duchess Elisabeth Alexandrine of Mecklenburg-Schwerin, on 26 October 1921 in Arolsen. Nikolaus succeeded as Head of the House of Oldenburg in 1931, upon his father's death.

The marriage produced nine children:

• Anton Günther, Duke of Oldenburg (1923–2014)
• Princess Rixa of Oldenburg (1924–1939)
• Prince Peter Friedrich August of Oldenburg (1926–2016)
• Princess Eilika of Oldenburg (1928–2016)
• Duke Egilmar of Oldenburg (1934–2013)
• Duke Friedrich Wilhelm of Oldenburg (1936–2017)
• Duchess Altburg of Oldenburg (1938–2009)
• Duke Huno of Oldenburg (1940–2021)
• Duke Johann of Oldenburg (born 1940)

Princess Helena died in Rastede, Germany, in 1948.