Cornelius Sim (16 September 1951 – 29 May 2021) was a Bruneian prelate of the Catholic Church. He was Apostolic Vicar of Brunei from 2004 until his death. He was the apostolic prefect of Brunei from 1997 to 2004. He was born in Seria, Brunei.
Sim was the first Bruneian to be ordained to the priesthood. Pope Francis raised him to the rank of a cardinal on 28 November 2020, making him the first cardinal from the country.
Sim died at a hospital in Taoyuan, Taiwan on 29 May 2021 from cardiac arrest, aged 69. He was being treated for cancer at the time of his death.