East German swimmer who is considered one of the greatest backstrokers of all time. Undefeated in major backstroke competitions between 1967 and 1974, Matthes set 16 world records and won eight Olympic medals.

At the 1968 Olympic Games in Mexico City, Matthes won gold medals in both the 100-metre and 200-metre backstroke, a feat he repeated at the 1972 Olympic Games in Munich. He swam the first leg of the 4 × 100-metre medley relay in world record times in both 1968 and 1972, leading the East German team to silver medals. Matthes' swimming style—characterized by a deceptively casual but powerful stroke, a long follow-through, and exceptional timing—lent itself well to other strokes, and he won a bronze medal at the 1972 Games in the 4 × 100 freestyle. Between 1967 and 1973, Matthes took the 100-metre backstroke world record from 58.4 to 56.30 seconds and the 200-metre mark from 2:07.9 to 2:01.87.

Weakened by health problems and distracted by the demands of being an East German celebrity, Matthes won only a bronze in the 100-metre backstroke at the 1976 Olympic Games in Montreal and did not place in the 200-metre. After the 1976 Games, he married his teammate Kornelia Ender (Ender, Kornelia).