The 35-year-old, who this year became the most successful sailor in Olympic history, had previously won the award in 1998, 2002 and 2008.
Gold in the Finn class at London 2012 took his Olympic tally to four golds and a silver, making him the first ever sailor to win medals at five different Games.
Also nominated for the male award were Australians Tom Slingsby, the 49er pairing of Nathan Outteridge and Iain Jensen and the 470 crew of Mat Belcher and Malcolm Page who all claimed Olympic gold in Weymouth this summer.
"Winning the World Sailor of the Year award is a huge honour, especially for everyone who has helped me," Ainslie said.
"There is a huge team in the background from family, friends, coaches and sponsors who helped make it happen. It is a huge honour to be part of such a group of exceptional sailors who were put forward for this award."
Britain's Paralympic gold medal-winner Helena Lucas and windsurfing youth world and European champion Saskia Sills were among the nominees in the female category that was won by China's Lijia Xu, the 2012 gold medallist in the laser radial class.
"Sailing has given me the chance to chase my dreams and the stage to show my potential," said Xu, who this year became the first Asian competitor to win an Olympic gold in a dinghy sailing boat.
"It has provided me with the opportunity to see, feel and explore the world. Sailing leads me to a path of a better life, a life full of vitality, excitement and joyful experiences."
- Sports & Recreation
- Nathan Outteridge