Rômulo Duncan Arantes Filho (usually Rômulo Arantes; June 12, 1957 – June 10, 2000) was a Brazilian swimmer and actor. He won a bronze medal in the 100-metre backstroke at the 1978 World Aquatics Championships and four medals at the Universiades (1977 and 1981) and Pan American Games (1979). He also competed in eight events at the 1972, 1976 and 1980 Summer Olympics with the best achievement of fifth place in the 4×100-metre medley relay in 1972.
He participated at the inaugural World Aquatics Championships in 1973 Belgrade, where he finished 7th in the 100-metre backstroke, breaking the South American record, with a time of 1:00.37. In the 200-metre backstroke, Arantes not classified to the final, but also broke the South American record, with a time of 2:12.98.
He was at the 1975 World Aquatics Championships in Cali. In the 100-metre backstroke, he finished 10th, with a time of 1:00.30, far from his personal best at this moment, the South American record (58.61 seconds). In the 4×100-metre medley, he finished 9th, with a time of 4:01.99, along with Sérgio Pinto Ribeiro, Heliani dos Santos and Ruy de Oliveira. Arantes had contracted a virus that made him stop his training for a month, which hurt his results in this World Championships.