Ket Sivan (born February 6, 1981) is a Cambodian swimmer, who specialized in sprint freestyle events. Ket qualified for the women's 50 m freestyle, by receiving a Universality place from FINA in an entry time of 34.68. She challenged six other swimmers in heat two, including 14-year-olds Sameera Al-Bitar of Bahrain and Christal Clashing of Antigua and Barbuda. She posted a lifetime best of 34.62 to save a seventh spot over Laos' Vilayphone Vongphachanh by nearly two seconds. Ket failed to advance into the semifinals, as she placed seventy-first overall out of 75 swimmers on the last day of preliminaries.