Canard held a three-point lead heading into the series finale and grabbed the Progressive Direct Holeshot Award at the start of the main event, with Monster Energy/Pro Circuit/Kawasaki star Villopoto in third place.
Villopoto's team-mate Branden Jesseman then took over the lead on the opening lap, with Canard and Villopoto settling into second and third, respectively.
The win and the championship would ultimately be decided at the end of lap four as both Villopoto and Canard overtook Jesseman.
With Villopoto leading, Canard dived for the inside and made contact with Villopoto, sending the multiple Lites champion off the track.
Canard kept his balance and took over sole possession of the lead and walked away with the first professional AMA championship of his career.
"I really didn’t mean to take him out," claimed Canard, a four-time winner on the season. "I think that’s racing and I would expect him to do the same to me if it came down to this last race. I really wanted this championship since I was like three years old. I just trained hard all week long and I can’t thank my team enough for getting this championship."
Jesseman finished second while Canard's Torco Fuels Honda team-mate Josh Grant was third.
AMA Supercross Class Results, St. Louis
1. Kevin Windham, Centreville, Miss., Honda
2. Chad Reed, Tampa, Fla., Yamaha
3. Andrew Short, Smithville, Texas, Honda
4. Nathan Ramsey, Menifee, Calif., Yamaha
5. Thomas Hahn, Decatur, Texas, Kawasaki
6. Davi Millsaps, Cairo, Ga., Honda
7. Justin Brayton, Murrieta, Calif., KTM
8. Paul Carpenter, Ithaca, N.Y., Honda
9. Travis Preston, Hesperia, Calif., Kawasaki
10. Jason Thomas, Melrose, Fla., Honda
AMA Supercross Class Season Standings:
1. Chad Reed, Tampa, Fla., Yamaha, 318
2. Kevin Windham, Centreville, Miss., Honda, 305
3. Davi Millsaps, Cairo, Ga., Honda, 244
4. Andrew Short, Smithville, Texas, Honda, 241
5. Joshua Hill, Yoncalla, Ore., Yamaha, 196
6. Tim Ferry, Largo, Fla., Kawasaki, 190
7. Nathan Ramsey, Menifee, Calif., Yamaha, 173
8. David Vuillemin, Murrieta, Calif., Suzuki, 146
9. Paul Carpenter, Ithaca, N.Y., Honda, 136
10. Nick Wey, Dewitt, Mich., KTM, 131
AMA Supercross Lites Class Results, St. Louis
1. Trey Canard, Elk City, Okla., Honda
2. Branden Jesseman, New Brighton, Pa., Kawasaki
3. Josh Grant, Riverside, Calif., Honda, 71
4. Ryan Villopoto, Poulsbo, Wash., Kawasaki
5. Ryan Morais, Murrieta, Calif., Yamaha
6. Kyle Chisholm, Seminole, Fla., Kawasaki
7. Ryan Sipes, Vine Grove, Ken., KTM, 70
8. Nico Izzi, Saint Clair., Mich., Suzuki
9. Matt Goerke, Lake Helen, Fla., KTM
10. Billy Payne, Simi Valley, Calif., Honda, 60
Eastern Regional AMA Supercross Lites Class Season Standings:
1. Trey Canard, Elk City, Okla., Honda, 147
2. Ryan Villopoto, Poulsbo, Wash., Kawasaki, 137
3. Nico Izzi, Saint Clair., Mich., Suzuki, 99
4. Branden Jesseman, New Brighton, Pa., Kawasaki, 94
5. Josh Grant, Riverside, Calif., Honda, 91
6. Tyler Bowers, Danville, Ken., Yamaha, 86
7. Ryan Morais, Murrieta, Calif., Yamaha, 84
8. Ryan Sipes, Vine Grove, Ken., KTM, 84
9. Martin Davalos, Cairo, Ga., KTM, 73
10. Billy Payne, Simi Valley, Calif., Honda, 71
