He edged out Women's Rugby World Cup winner Ellie Kildunne and Formula One world champion Lando Norris.
McIlroy became only the sixth man to complete golf's career Grand Slam with a long-awaited victory at the Masters in April.
He also helped inspire Europe to a dramatic Ryder Cup victory over the United States at Bethpage Black, despite being targeted by persistent abuse from the American fans, and won the prestigious Players Championship for the second time.
"2025 has been the year I made my dreams come true," McIlroy said.
"From Augusta to the Ryder Cup and everything in between. It's the year dreams are made of."
The 36-year-old became only the third Northern Irish winner of the prize after former jockey AP McCoy and 1972 Olympic pentathlon champion Mary Peters.
It was a double success for McIlroy as the European Ryder Cup side were named the Team of the Year.
The other nominees for the main prize were 18-year-old darts world champion Luke Littler, as well as England's Women's Euro 2025 winners Hannah Hampton and Chloe Kelly.
List of winners
Sports Personality of the Year: Rory McIlroy
Team of the Year: European Ryder Cup team win public vote
Lifetime Achievement award: Thierry Henry
Helen Rollason award: Sergio Aguiar and David Stancombe
World Sport Star: Armand Duplantis
Coach of the Year: Sarina Wiegman
Young Sports Personality of the Year: Michelle Agyemang