Calls on the league to change eligibility criteria were rejected in June when West Coast sensation Reid and Western Bulldogs gun Darcy were both banned for two matches.
The AFL maintained a "fairest" component should be maintained in the criteria.
It left Dempsey a clear standout among the competition's eligible young talents, with his outstanding form for the premiership-contending Cats franked in a runaway Rising Star win.
Dempsey polled 52 of a possible 55 votes, with North Melbourne's George Wardlaw (43) second and the Brisbane Lions' Kai Lohmann (21) third.
Dempsey received the Ron Evans Medal and $20,000 in prize money after polling a maximum five votes from nine of the 11-member selection panel, chaired by AFL chief executive Andrew Dillon.
Originally a rookie draft selection, Dempsey managed just seven games as a fringe player over his first two seasons but has become a key figure in the Cats' rise back into the top four this year.
The 21-year-old has kicked 21 goals in 23 games, averaging 17.6 disposals, 5.4 score involvements and 1.0 goal assists as an influential player in the front half of the ground and on the wing.
Dempsey is the second Geelong player to win the Rising Star award after club great Joel Selwood in 2007.
Ollie Dempsey turns two Tigers defenders inside out during their round-12 clash in Geelong. (Julian Smith/AAP PHOTOS)
Reid and Darcy were both handed two-match suspensions over separate incidents in round 12.
No.1 draft pick Reid was banned for rough conduct over a dangerous tackle on St Kilda's Darcy Wilson, who finished fourth in the Rising Star award with 15 votes.
Bulldogs father-son recruit Darcy was banned for his late hit on Collingwood defender Brayden Maynard.
Reid was named the AFL Players Association's best first-year player ahead of Wilson and Melbourne winger Caleb Windsor.
North Melbourne's prolific Harry Sheezel won the AFL Coaches Association's best young player award, which recognises players based on performances over their first two seasons.
Sheezel was the Rising Star winner last year at the end of an outstanding debut season.
2024 AFL RISING STAR AWARD:
1. Ollie Dempsey (Geelong) - 52 votes
2. George Wardlaw (North Melbourne) - 43 votes
3. Kai Lohmann (Brisbane Lions) - 21 votes
4. Darcy Wilson (St Kilda) - 15 votes
5. Colby McKercher (North Melbourne) - 12 votes
