This is the complete list of all 82 fighters in UFC 2009 Undisputed (80 immediately available, 2 DLC characters). If a fighter has two letters in parenthesis next to his name, that simply means that he can fight in two weight classes, so for instance for Brandon Vera has (LH) which means he can also fight as a Light Heavyweight. Depending on the fighter he can either fight up or down in weight classes so some fighters can go up a weight and some can come down a weight.

Heavyweights
1. Antonio Rodrigo Nogueira
2. Brock Lesnar
3. Frank Mir
4. Brandon Vera (LH)
5. Gabriel Gonzaga
6. Cain Velasquez
7. Cheick Kongo
8. Eddie Sanchez
9. Heath Herring
10. Andrei Arlovski
11. Mirko Crocop
12. Fabricio Werdum
13. Tim Sylvia
14. Mark Coleman
15. Antoni Hardonk
16. Justin McCully

Light Heavyweights
1. Chuck Lidell
2. Quinton “Rampage” Jackson
3. Forrest Griffin
4. Tito Ortiz
5. Keith Jardine
6. Wanderlei Silva
7. Mauricio “Shogun” Rua
8. Lyoto Machida
9. Rashad Evans
10. Stephan Bonnar
11. James Irvin
12. Wilson Gouveia (MW)
13. Houston Alexander
14. Kazuhiro Nakamura
15. Thiago Silva
16. Tim Boetsch
17. Ryan Bader (DLC)

Middleweights
1. Anderson Silva (LH)
2. Rich Franklin (LH)
3. Dan Henderson (LH)
4. Michael Bisping (LH)
5. Kendall Grove
6. Chris Leben
7. Jason MacDonald
8. Nate Marquardt
9. Drew McFedries
10. Ricardo Almeida
11. Evan Tanner
12. Yushin Okami
13. Demian Maia
14. Martin Kampmann (WW)
15. Amir Sadollah (WW)
16. Thales Leites

Welterweights
1. Georges St-Pierre
2. Matt Hughes
3. Matt Sera (LW)
4. Jon Fitch
5. Karo Parisyan
6. Josh Koscheck
7. Diego Sanchez
8. Mike Swick (MW)
9. Marcus Davis
10. Thiago Alves
11. Chris Lytle
12. Ben Saunders
13. Josh Burkman
14. Kyle Bradley
15. Matt Arroyo
16. Anthony Johnson

Lightweights
1. BJ Penn (WW)
2. Sean Sherk (WW)
3. Kenny Florian
4. Roger Huerta
5. Joe Stevenson
6. Mac Danzig
7. Nathan Diaz
8. Spencer Fisher
9. Tyson Griffin
10. Gray Maynard
11. Thiago Tavares
12. Joe Lauzon
13. Rich Clementi
14. Mark Bocek
15. Hermes Franca
16. Frank Edgar
17. Efrain Escudero (DLC)