Tun Pehin Sri Datuk Patinggi Abang Haji Muhammad Salahuddin bin Abang Barieng (born Louis anak Barieng; Jawi: ابڠ محمد صلاح الدين بن ابڠ باريئڠ; 27 August 1921 – 28 January 2022) was a Malaysian politician who served as the third Yang di-Pertua Negeri of Sarawak from 1977 to 1981, and as the sixth Yang di-Pertua Negeri from 2001 to 2014. He was the first Yang di-Pertua Negeri to hold the post twice, as well as the oldest elected to the office.