| Sithean Reachea Central Khmer: សិទ្ធានរាជា | |
| Succession: | King of the Khmer Empire |
| Reign: | 1346–1347 |
| Predecessor: | Nippean Bat |
| Successor: | Lompeng Reachea |
| Royal House: | Trasak Paem |
| Father: | Trasak Paem |
| Mother: | Chantreavattey |
| Birth Date: | 1309 |
Sithean Reachea (Central Khmer: សិទ្ធានរាជា,) or Sidhanta Raja (full regnal name: Brahat Pada Samdach Sdach Rajankariya Brhat Sidhanta Rajadhiraja Ramadipathi) was ruler of the Khmer Empire from 1346 to 1347. Born in 1294, he was the second and youngest son of Trasak Paem. According to the Royal Chronicles, he succeeded his brother Nippean Bat and reigned for three or six months before resigning in favor of his nephew Lompeng Reachea. After his abdication he bore the ceremonial title of "Maha Upayuvaraja" (Retired Great King) and died on an unknown date.