Sebastian Sim (Chinese: 沈岳川; pinyin: Shěn Yuè Chuān; born 2 October 1966) is a Singaporean author, including of wuxia novels.

He won the 2017 Epigram Books Fiction Prize for best original and unpublished novel in the English language written by a Singaporean citizen, Singapore permanent resident or Singapore-born writer for his novel, The Riot Act.

Sim studied at Hwa Chong Junior College and was awarded the Public Service Commission scholarship.

[5] His second English novel, The Riot Act, won the 2017 Epigram Books Fiction Prize.

won the 2021 edition of Epigram Books Fiction Prize, shared with Boey Meihan's The Formidable Miss Cassidy.