According to Official Guinness Records,
The most Olympic equestrian medals won by an individual is 10, achieved by Isabell Werth (Germany) from 1992 to 2000 and again in 2008 and 2016.Isabell has won six gold medals and four silver across five different Olympic Games.
For a complete list of 2016 records, please visit 2016 Guinness Records in Brazil.