Sien de la Mar-Klopper
- Birthday: 1881-03-15
- Deathday: 1944-07-10
- Place of birth: Amsterdam
- Also know as: Sien de la Mar
Clasina Margaretha ‘Sien’ de la Mar-Klopper (1881-1944) was a Dutch actress. She was married to actor Nap de la Mar and mother of popular actress, singer and comedienne Fien de la Mar.
