Princess Sasibongse Prabai or Phra Chao Boromwongse Ther Phra Ong Chao Sasibongse Prabai (RTGS: Sasiphong Praphai) (Thai: พระเจ้าบรมวงศ์เธอ พระองค์เจ้าศศิพงศ์ประไพ) (26 April 1881 – 31 May 1934), was a Princess of Siam (later Thailand.

She was a member of Siamese royal family.

She is a daughter of Chulalongkorn, King Rama V of Siam.

Her mother was Chao Chom Manda Chan, daughter of Lord (Phraya) Rajasam Bharakorn.

Princess Sasibongse Prabai died on 31 May 1934, at the age of 53.