Hendrika Anna Maria "Ria" van der Horst (born 10 August 1932) is a former Dutch backstroke swimmer who participated in the 1948 and 1952 Summer Olympics. In 1948, she was fifth in 100 m backstroke, and in 1952 she was disqualified for an incorrect turn. She won the gold medal in the same event at the 1950 European Aquatics Championships.