Petronella Theodora Maria "Ellen" Bontje (born June 11, 1958 in Hilversum, North Holland) is an equestrian from The Netherlands, who won the silver medal in the Team Dressage Event at the 2000 Olympic Games in Sydney, Australia. She did so alongside Anky van Grunsven, Coby van Baalen, and Arjen Teeuwissen. In the individual competition Bontje finished in sixth position.
Eight years earlier, at the 1992 Olympic Games in Barcelona, Spain, Bontje was also a member of the Dutch team that won the silver medal in the Team Dressage Competition. She competed in three Summer Games for her native country, starting at the 1988 Olympics in Seoul, South Korea.
She has won eight silver medals and one bronze medal in team dressage at various championships.