The 29-year-old won two individual gold medals and a team silver at the World Equestrian Games in Caen during the summer, while also claiming victory at the dressage World Cup finals in Lyon in April.
Dujardin – who currently holds freestyle and special titles at Olympic, European and World level – fought off competition from Winter Olympic champion Lizzy Yarnold, who was named runner-up, as well as European 10,000m champion Jo Pavey, who came third.
“I have an incredible relationship with Valegro, working with him for eight years,” said Dujardin. “He is like my dance parner and he should be receiving the award with me but he is at home in his stable.
“My next big competition is the World Cup final in Las Vegas next year and then the Europeans and Olympics.”
Swimmer Fran Halsall, squash player Laura Massaro and track cyclist Joanna Rowsell were all nominated for the title.
Gymnast Claudia Fragapane, meanwhile, secured the young sportswoman gong after collecting four gold medals at this year’s Commonwealth Games in Glasgow, while England’s World Cup-winning rugby union side won the team of the year accolade.