Dieung Anak Manggang (born 11 April 1981) is a Malaysian former swimmer, who specialised in long-distance freestyle and in butterfly events.

[2][3] Manggang competed in a long-distance freestyle double at the 2000 Summer Olympics in Sydney.

Swimming in heat two, he rounded out the field to last place in 4:03.77, more than three seconds off his entry time.

[6][7] Nearly a week later, in the 1500 m freestyle, Manggang challenged five other swimmers in the same heat, including 18-year-old Jonathan Duncan of New Zealand.

He held off Duncan by more than half the body length to take a third spot and thirty-sixth overall in a time of 16:02.11.