Thum Ping Tjin (Chinese: 覃炳鑫; pinyin: Tán Bǐng Xīn) (born 17 December 1979), also known as PJ Thum, is a Singaporean historian, journalist, podcaster, activist and former swimmer. Thum was a national swimmer who participated in the 1996 Summer Olympics, and was the first Singaporean to swim the English Channel.