Sunandha Kumariratana (Thai: สุนันทากุมารีรัตน์; rtgs: Sunantha Kumarirat, 10 November 1860 – 31 May 1880) was a daughter of King Mongkut (Rama IV) and Princess Consort Piam. Her given name is Princess Sunandha Kumariratana (พระองค์เจ้าสุนันทากุมารีรัตน์). She was a half-sister and the first queen consort (พระบรมราชเทวี) and one of four queens of King Chulalongkorn (Rama V,of Siam,now Thailand), two of which were her full-sibling younger sisters, Queen Savang Vadhana and Queen Saovabha Bhongsi.
The queen and her daughter drowned when the royal boat capsized while on the way to the Bang Pa-In Royal Palace (Summer palace). Despite the presence of many onlookers, they were forbidden on pain of death to touch the queen – not even to save her life. The grief-stricken Chulalongkorn later erected a memorial to her and his unborn child at the Bang Pa-In Palace.